Liquid crystal display device

ABSTRACT

It is an object of the present invention to apply a sufficient electrical field to a liquid crystal material in a horizontal electrical field liquid crystal display device typified by an FFS type. In a horizontal electrical field liquid crystal display, an electrical field is applied to a liquid crystal material right above a common electrode and a pixel electrode using plural pairs of electrodes rather than one pair of electrodes. One pair of electrodes includes a comb-shaped common electrode and a comb-shaped pixel electrode. Another pair of electrodes includes a common electrode provided in a pixel portion and the comb-shaped pixel electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/848,247, filed Aug. 2, 2010, now allowed, which is a continuation ofU.S. application Ser. No. 11/566,005, filed Dec. 1, 2006, now U.S. Pat.No. 7,773,182, which claims the benefit of a foreign priorityapplication filed in Japan as Serial No. 2005-350147 on Dec. 5, 2005,all of which are incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device. Inparticular, the present invention relates to a liquid crystal displaydevice having a wide viewing angle.

2. Description of the Related Art

A display device includes a self-light emitting display device and alight receiving display device. A liquid crystal display device is themost typical light receiving display device. A driving method for liquidcrystal in a liquid crystal display device includes a verticalelectrical field type in which voltage is applied perpendicularly to asubstrate and a horizontal electrical field type in which voltage isapplied approximately parallel to the substrate. Each of a verticalelectrical field type and a horizontal electrical field type has anadvantage and disadvantage. For example, a horizontal electrical fieldtype has characteristics such as a wide viewing angle, high contrast,high gradation display, and the like compared with a vertical electricalfield type typified by a TN type, and is used for a monitor ortelevision. These kinds of liquid crystal display devices coexist in thefield of liquid crystal, and product development has been made. Inaddition, each of a liquid crystal material for a horizontal electricalfield type and a liquid crystal material for a vertical electrical fieldtype is developed and has different material characteristics accordingto a direction of applied voltage.

In addition, a horizontal electrical field liquid crystal display deviceincludes an IPS (In-Plane Switching) type and an FFS (Fringe FieldSwitching) type. In an IPS type, a pixel electrode having a comb-shapeor a slit and a common electrode having a comb-shape or a slit arealternately arranged and an electrical field approximately parallel to asubstrate is generated between the pixel electrode and the commonelectrode, whereby a liquid crystal display device is driven (see PatentDocument 1). On the other hand, in an FFS type, a pixel electrode havinga comb-shape or a slit is placed over a common electrode which having aplane-shape that is formed in a whole pixel portion. An electrical fieldapproximately parallel to a substrate is generated between the pixelelectrode and the common electrode, whereby a liquid crystal displaydevice is driven.

It is shown that an FFS liquid crystal display device has hightransmittance, a wide viewing angle, low power consumption, and nocrosstalk (see Non-Patent Document 1).

-   [Patent Document 1] Japanese Published Patent Application No.    H9-105918-   [Non-Patent Document 1] Ultra-FFS TFT-LCD with Super Image Quality    and Fast Response Time, 2001 The Society For Information Display pp.    484-487

In a horizontal electrical field type liquid crystal display devicewhich is typified by a conventional horizontal electrical field typeliquid crystal display device, an electrical field applied to a liquidcrystal material is not sufficient. This is because an electrical fieldis not well applied to a liquid crystal material which is right above acommon electrode and a pixel electrode.

In addition, a wide viewing angle technique using a horizontalelectrical field type such as an IPS type or an FFS type is used mostlyfor television; therefore, the technique is applied only to atransmissive type. However, a reflective type or a semitransmissive typeis needed when reducing power consumption or outdoors use is required.However, a reflective or a semitransmissive type is realized by using avertical electrical field type typified by a TN type.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide astructure of a horizontal electrical field type liquid crystal displaydevice, in which a sufficient electrical field is applied to a liquidcrystal material.

In addition, it is an object of the present invention to provide aliquid crystal display device with a wide viewing angle and lesscolor-shift, and which can display an image favorably recognized bothindoors and outdoors.

In view of the foregoing problems, in the present invention, anelectrical field is applied to a liquid crystal material using pluralpairs of electrodes rather than one pair of electrodes. The one pair ofelectrodes includes a comb-shaped common electrode and a comb-shapedpixel electrode. Another pair of electrodes includes a common electrodeformed in a pixel portion and a comb-shaped pixel electrode. The commonelectrode provided in the pixel portion can be provided in a regionexcept the thin film transistor. In addition, the common electrodeprovided in the pixel portion may be comb-shaped. In such a liquidcrystal display device, an electrical field applied to a liquid crystalmaterial can be controlled by using another pair of electrodes, as wellas the one pair of electrodes.

A liquid crystal display device of the present invention includes afirst region in which display is conducted by light transmission and asecond region in which a display is conducted by light reflection. Inaddition, a liquid crystal layer includes a liquid crystal moleculerotating in a plane parallel to an electrode surface, that is, parallelto a substrate, when an electric potential difference is generatedbetween two electrodes in a liquid crystal element which are providedbelow the liquid crystal layer.

Note that in the present invention, the phrase “rotation parallel to anelectrode surface” means that a parallel rotation which includes adeviation unrecognizable by human eyes. In other words, the phrase“rotation parallel to an electrode surface” means that a rotation whichmainly includes a vector component parallel to the electrode surface butalso includes a few vector component normal to the electrode surface.

When an electric potential difference is generated between electrodes803 and 804 provided below a liquid crystal layer 801, a liquid crystalmolecule 802 contained in the liquid crystal layer 801 rotates by aneffect of a horizontal electrical field. A state shown in FIG. 77Achanges into that shown in FIG. 77B or the state shown in FIG. 77Bchanges into that shown in FIG. 77A, as the liquid crystal molecule 802rotates. FIGS. 77A and 77B are cross-sectional views. The rotation seenfrom above is shown by an arrow in FIG. 77C.

In a similar manner, when an electric potential difference is generatedbetween electrodes 9803 and 9805 and between electrodes 9804 and 9805provided below a liquid crystal layer 9801, a liquid crystal molecule9802 contained in the liquid crystal layer 9801 rotates by an effect ofa horizontal electrical field and a state shown in FIG. 112A changesinto that shown in FIG. 112B or the state shown in FIG. 112B changesinto that shown in FIG. 112A as the liquid crystal molecule 9802rotates. FIGS. 112A and 112B show cross-sectional views. The rotationseen from above is shown by an arrow in FIG. 112C.

Note that a positional relationship or the like of the electrodes 803and 804 is not limited to those shown in FIGS. 77A to 77C.

In a similar manner, a positional relationship or the like of theelectrodes 9803, 9804, and 9805 is not limited to those shown in FIGS.112A to 112C.

In the first region described above, one pair of electrodes providedbelow a liquid crystal layer includes electrodes provided in differentlayers. In the first region, two electrodes in a liquid crystal elementare provided below the liquid crystal layer and the electrodes areprovided in different layers. One of the electrodes serves as areflector or a reflector is provided so as to overlap with theelectrodes, whereby light is reflected. In the second region, twoelectrodes in a liquid crystal element are formed below the liquidcrystal layer. Both of the electrodes are transparent and provided overone layer or over different layers with an insulating layer interposedtherebetween.

A specific structure of the present invention is shown below.

One mode of the present invention is a liquid crystal display device,including a first common electrode, an insulating layer provided overthe first common electrode, a pixel electrode and a second commonelectrode provided over the insulating layer, and a liquid crystalmaterial provided over the pixel electrode and the second commonelectrode, in which tilting of the liquid crystal material is controlledby an electrical field between the pixel electrode and the first commonelectrode and an electrical field between the pixel electrode and thesecond common electrode.

Another mode of the present invention is a liquid crystal displaydevice, including an insulating substrate, a thin film transistor formedover the insulating substrate, a first common electrode provided in thesame layer as a semiconductor layer of the thin film transistor, aninsulating layer provided to cover the first common electrode, a pixelelectrode and a second common electrode provided over the insulatinglayer, and a liquid crystal material provided over the pixel electrodeand the second common electrode, in which the pixel electrode iscontrolled by the thin film transistor, the first common electrode andthe second common electrode are electrically connected, and tilting ofthe liquid crystal material is controlled by an electrical field betweenthe pixel electrode and the first common electrode and an electricalfield between the pixel electrode and the second common electrode.

Another mode of the present invention is a liquid crystal displaydevice, including an insulating substrate, a thin film transistor formedover the insulating substrate, a first common electrode provided in thesame layer as source and drain electrodes of the thin film transistor, aconductive layer connected to the first common electrode, an insulatinglayer provided over the first common electrode and the conductive layer,a pixel electrode and a second common electrode provided over theinsulating layer, and a liquid crystal material provided over the pixelelectrode and the second common electrode, in which tilting of theliquid crystal material is controlled by an electrical field between thepixel electrode and the first common electrode and an electrical fieldbetween the pixel electrode and the second common electrode.

Another mode of the present invention is a liquid crystal displaydevice, including an insulating substrate, a thin film transistor formedover the insulating substrate, a first common electrode provided in thesame layer as a semiconductor layer of the thin film transistor, aconductive layer connected to the first common electrode, an insulatinglayer provided over the first common electrode and the conductive layer,a pixel electrode and a second common electrode provided over theinsulating layer, and a liquid crystal material provided over the pixelelectrode and the second common electrode, in which tilting of theliquid crystal material is controlled by an electrical field between thepixel electrode and the first common electrode and an electrical fieldbetween the pixel electrode and the second common electrode.

In a structure of the present invention, the thin film transistor caninclude a crystalline semiconductor layer.

In a structure of the present invention, a passivation layer providedover the first common electrode and the thin film transistor, a colorfilter provided over the first common electrode with the passivationlayer therebetween, and a black matrix provided over the thin filmtransistor with the passivation layer therebetween can be furtherincluded.

In a structure of the present invention, a passivation layer providedover the first common electrode and the thin film transistor, a colorfilter provided over the first common electrode and the thin filmtransistor with the passivation layer therebetween, a counter substrateprovided to face the insulating substrate, and a black matrix providedover the thin film transistor can be further included.

In a structure of the present invention, a passivation layer providedover the thin film transistor, a color filter provided over thepassivation layer, a first common electrode provided over the colorfilter, and a black matrix provided over the thin film transistor overthe passivation layer can be further included.

Another mode of the present invention is a liquid crystal displaydevice, including an insulating substrate, a gate electrode formed overthe insulating substrate, a first common electrode formed in the samelayer as the gate electrode, an insulating layer provided to cover thegate electrode and the first common electrode, a semiconductor layerprovided over the gate electrode with the insulating layer therebetween,source and drain electrodes formed in the semiconductor layer, aconductive layer provided in the same layer as the source and drainelectrodes to be in contact with the first common electrode, a pixelelectrode connected to one of the source and drain electrodes, a secondcommon electrode connected to the first common electrode with theconductive layer therebetween, and a liquid crystal material providedover the pixel electrode and the second common electrode, in whichtilting of the liquid crystal material is controlled by an electricalfield between the pixel electrode and the first common electrode and anelectrical field between the pixel electrode and the second commonelectrode.

One mode of the present invention is a liquid crystal display device,including an insulating substrate, a gate electrode formed over theinsulating substrate, a conductive layer formed in the same layer as thegate electrode, a first common electrode provided in contact with theconductive layer, an insulating layer provided to cover the gateelectrode and the first common electrode, a semiconductor layer providedover the gate electrode with the insulating layer therebetween; sourceand drain electrodes formed in the semiconductor layer, a pixelelectrode connected to one of the source and drain electrodes, a secondcommon electrode connected to the first common electrode with theconductive layer therebetween, and a liquid crystal material providedover the pixel electrode and the second common electrode, in whichtilting of the liquid crystal material is controlled by an electricalfield between the pixel electrode and the first common electrode and anelectrical field between the pixel electrode and the second commonelectrode.

In a structure of the present invention, the semiconductor layer canhave an amorphous semiconductor layer.

In a structure of the present invention, a passivation layer providedover the first common electrode, a color filter provided over the firstcommon electrode with the passivation layer therebetween, and a blackmatrix provided over the source and drain electrodes can be furtherincluded.

In a structure of the present invention, a passivation layer providedover the first common electrode and the gate electrode; a color filterprovided over the source and drain electrodes and over the first commonelectrode with the passivation layer therebetween, a counter substrateprovided to face the insulating substrate, and a black matrix providedover the counter substrate can be further included.

In a structure of the present invention, the pixel electrode can becomb-shaped.

In a structure of the present invention, the first common electrode canbe comb-shaped.

In a structure of the present invention, the second common electrode canbe comb-shaped.

In a structure of the present invention, the pixel electrode may beformed of a transparent material.

In a structure of the present invention, the first common electrode maybe formed of a transparent material.

In a structure of the present invention, the second common electrode maybe formed of a transparent material.

According to the present invention, an electrical field can be appliedsufficiently to a liquid crystal material using two or more pairs ofelectrodes. Then, tilting of the liquid crystal material can becontrolled by electrical fields generated by two pairs of electrodes,whereby gray-scale display can be conducted.

In addition, according to the present invention, an image with a wideviewing angle and less color-shift due to the angle at which the displayscreen is watched, and which is favorably recognized outdoors in the sunand dark indoors (or outdoors at night) can be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 2 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 3 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 4 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 5 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIGS. 6A to 6C are cross-sectional views of a liquid crystal displaydevice of the present invention;

FIGS. 7A to 7C are cross-sectional views of a liquid crystal displaydevice of the present invention;

FIGS. 8A to 8C are cross-sectional views of a liquid crystal displaydevice of the present invention;

FIGS. 9A to 9C are cross-sectional views of a liquid crystal displaydevice of the present invention;

FIGS. 10A to 10C are cross-sectional views of a liquid crystal displaydevice of the present invention;

FIGS. 11A to 11C are cross-sectional views of a liquid crystal displaydevice of the present invention;

FIGS. 12A to 12C are cross-sectional views of a liquid crystal displaydevice of the present invention;

FIG. 13 is a top view of a liquid crystal display device of the presentinvention;

FIG. 14 is a top view of a liquid crystal display device of the presentinvention;

FIG. 15 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 16 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 17 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 18 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 19 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 20 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 21 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 22 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 23 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 24 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 25 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 26 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 27 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 28 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 29 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 30 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 31 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 32 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 33 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 34 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 35 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 36 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 37 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 38 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 39 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 40 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 41 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 42 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 43 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 44 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 45 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 46 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 47 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 48 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 49 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 50 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 51 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 52 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 53 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 54 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 55 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 56 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 57 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 58 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 59 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 60 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 61 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 62 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 63 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 64 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 65 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 66 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 67 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 68 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 69 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 70 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 71 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 72 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 73 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 74 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 75 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 76 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIGS. 77A to 77C are views of a liquid crystal display device of thepresent invention;

FIG. 78 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 79 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 80 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 81 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 82 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 83 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 84 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 85 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 86 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 87 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 88 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 89 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 90 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 91 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 92 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 93 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 94 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 95 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 96 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 97 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 98 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 99 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 100 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 101 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 102 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 103 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 104 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 105 is a cross-sectional view of a liquid crystal display device ofthe present invention;

FIG. 106 is a view of a liquid crystal display device of the presentinvention;

FIGS. 107A to 107D are views of a liquid crystal display device of thepresent invention;

FIG. 108 is a view of a liquid crystal display device of the presentinvention;

FIGS. 109A and 109B are cross-sectional views of a liquid crystaldisplay device of the present invention;

FIGS. 110 A and 110B are views of a liquid crystal display device of thepresent invention;

FIGS. 111A to 111H are views of examples of electronic appliances towhich the present invention is applied; and

FIGS. 112A to 112C are cross-sectional views of a liquid crystal displaydevice of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the embodiment modes of the present invention is describedwith reference to the accompanying drawings. The present invention canbe carried out in many different modes, and it is easily understood bythose skilled in the art that modes and details herein disclosed can bemodified in various ways without departing from the purpose and thescope of the present invention. Accordingly, the present inventionshould not be interpreted as being limited to the description of theembodiment modes to be given below. Note that like portions in thedifferent drawings are denoted by the like reference numerals whendescribing embodiment modes with reference to the drawings, and repeatedexplanations thereof are omitted.

In the present invention, a type of applicable transistor is notlimited. It is thus possible to apply a thin film transistor (TFT) usinga non-single crystalline semiconductor film typified by amorphoussilicon or polycrystalline silicon, a MOS transistor, a junction typetransistor, a bipolar transistor, which are formed using a semiconductorsubstrate or an SOI substrate a transistor using an organicsemiconductor or a carbon nanotube, or the like. In addition, the typeof substrate over which a transistor is provided is not limited and thetransistor can be formed over a single crystalline substrate, an SOIsubstrate, a glass substrate, or the like.

In the present invention, a connection is synonymous to an electricalconnection. Accordingly, in a structure disclosed in the presentinvention, another element which enables electrical connection (such asdifferent element, a switch, a transistor, a capacitor, a resistor, or adiode) may be interposed between elements having a predeterminedconnection relationship.

A switch shown in the present invention may be any switch such as anelectrical switch or a mechanical switch. It may be anything as long asit can control current flow. It may be a transistor, a diode, or a logiccircuit that is a combination thereof. Therefore, in the case of using atransistor as a switch, a polarity (conductivity) thereof is notparticularly limited because it operates as a mere switch. However, whenan off current is preferred to be small, a transistor of a polarity withsmall off current is desirably used. A transistor having an LDD region,a transistor having a multiage structure, and the like are given as atransistor with small off current. Further, it is desirable that anN-channel transistor is employed when a potential of a source terminalof the transistor serving as a switch is closer to the low potentialside power source (Vss, Vgnd, 0 V or the like), and a P-channeltransistor is desirably employed when the potential of the sourceterminal is closer to the high potential side power source (Vdd or thelike). This helps a transistor to easily serve as a switch as theabsolute value of the gate-source voltage can be increased. Note that aCMOS switch can also be applied by using both N-channel and P-channeltransistors.

As described above, a transistor of the present invention may be anytype of transistors and may be formed over any type of substrate.Therefore, all circuits driving a pixel may be formed over a glasssubstrate, a plastic substrate, a single crystalline substrate, an SOIsubstrate, or any other substrates. Alternatively, some of the circuitsdriving the pixel may be formed over one substrate while other circuitsmay be formed over another substrate. That is, not all of the circuitsare required to be formed over the same substrate. For example, a pixelportion and a gate line driver circuit may be formed with a TFT over aglass substrate while a signal line driver circuit (or a part thereof)may be formed over a single crystalline substrate, then, an IC chipthereof is connected to the glass substrate by COG (Chip On Glass).Alternatively, the IC chip may be connected to the glass substrate usingTAB (Tape Automated Bonding) or a printed board.

Note that an element arranged in a pixel is not specifically limited. Asa display element arranged in a pixel, any display element may be used,such as an EL (electroluminescence) element (also referred to as OLED(organic light emitting diode), an organic EL element, an inorganic EL,or the like), an element used in a field emission display (FED), an SED(Surface-conduction Electron-emitter Display) that is one kind of fieldemission display (FED), a liquid crystal display (LCD), a grating lightvalve (GLV), a plasma display (PDP), an electronic paper display, adigital micromirror device (DMD), or a piezoelectric ceramic display.

Note that a semiconductor device refers to a device having asemiconductor element such as a transistor or a diode. A display devicerefers to a device having a display element such as a liquid crystalelement or an EL element. A light emitting device refers to a devicehaving a light emitting element such that used in an EL element or FED.

Embodiment Mode 1

An example of a liquid crystal display device of the present inventionis described with reference to FIG. 78. In a liquid crystal displaydevice, a plurality of pixels is provided in matrix. An example of across-sectional structure of one pixel is shown in FIG. 78.

As shown in FIG. 78, a pixel includes a portion which conducts displayby reflecting light (reflective portion) 1001 and a portion whichconducts display by having light pass therethrough (transmissiveportion) 1002. In each region, an electrode serving as a pixel electrodeand an electrode serving as a common electrode are provided.

The electrode serving as a pixel electrode has a comb-shape or a slit.On the other hand, the electrode serving as a common electrode includesa portion which has a plain-shape and a portion having a comb-shape or aslit. However, it is not limited to this combination.

When voltage is supplied to the electrode serving as a pixel electrodeand the electrode serving as a common electrode, an electrical field isgenerated. The electrical field has many components parallel to asubstrate. A liquid crystal molecule rotates in a plane parallel to thesubstrate according to the electrical field. Thus, transmittance andreflectance of light can be controlled, thereby displaying a gray-scale.

When the electrode serving as a common electrode is provided in plural,it is desirably to form an opening (contact hole) in an insulating layeror overlap the electrodes in order to electrically connect theelectrodes to each other.

When the electrode serving as a pixel electrode and the electrodeserving as a common electrode are provided with an insulating layertherebetween, the overlapped portion can serve as a capacitor. Thecapacitor can serve as a holding capacitor for holding an image signal.

In the portion which conducts display by reflecting light (reflectiveportion) 1001, a reflective electrode is provided. A display isconducted by reflecting light by the reflective electrode. Thereflective electrode may serve as the common electrode as well. In sucha case, the reflective electrode may be connected to the commonelectrode to be supplied with voltage. Needless to say, the reflectiveelectrode and the common electrode may be separately provided. In such acase where the reflective electrode and the common electrode areseparated, the reflective electrode may be supplied with no voltage ormay be supplied with another voltage.

In the portion which conducts display by having light pass therethrough(transmissive portion) 1002, a transparent electrode may be provided. Adisplay is conducted by having light pass therethrough or through anaperture in the transparent electrode. The transparent electrode mayserve as the common electrode as well. In such a case, the transparentelectrode may be connected to the common electrode to be supplied withvoltage. Needless to say, the transparent electrode and the commonelectrode may be separately provided. In such a case where thetransparent electrode and the common electrode are separated, thetransparent electrode may be supplied with no voltage or may be suppliedwith another voltage. In addition, the transparent electrode may serveas the pixel electrode as well.

A structure shown in FIG. 78 is described. In the reflective portion1001, an electrode 9103 in a liquid crystal element and an electrode9305 in a liquid crystal element are overlapped with insulating layers9204 and 9304 therebetween. In the transmissive portion 1002, theelectrode 9103 in a liquid crystal element and an electrode 9104 in aliquid crystal element are overlapped with an insulating layer 9304therebetween.

In the reflective portion 1001 and the transmissive portion 1002, theelectrode 9103 in a liquid crystal element and an electrode 9105 in aliquid crystal element are alternately arranged.

The electrodes 9103 and 9105 in a liquid crystal element are formed tobe comb-shaped and the electrodes 9305 and 9104 in a liquid crystalelement are plain-shaped. However, it is not limited thereto. Theelectrodes 9305 and 9104 in a liquid crystal element may each have aslit-like aperture, a hole, or may be comb-shaped.

The electrode 9103 in a liquid crystal element serves as the pixelelectrode and the electrodes 9305, 9104, and 9105 in a liquid crystalelement serve as the common electrodes. However, it is not limitedthereto and the electrode 9103 in a liquid crystal element may serve asthe common electrode and the electrodes 9305, 9104, and 9105 in a liquidcrystal element may serve as the pixel electrodes.

It is desirable that each of the common electrodes be connectedelectrically by forming a contact hole in the insulating layer oroverlapping the electrodes each other.

The electrode 9305 in a liquid crystal element is formed of a conductivematerial which reflects light. Therefore, the electrode 9305 in a liquidcrystal element serves as the reflective electrode. In addition, theelectrode 9104 in a liquid crystal element is formed of a transparentmaterial which has light pass therethrough. Therefore the electrode 9104in a liquid crystal element serves as the transparent electrode.

The electrodes 9103 and 9105 in a liquid crystal element are desirablyformed of a material which is conductive as well as transparent. This isbecause they can contribute to a portion which displays an image whenthey can have light pass therethrough. Note that the electrodes 9103 and9105 in a liquid crystal element may be formed of a material whichreflects light. In such a case, even the transmissive portion 1002 canserve as the reflective portion since the transmissive portion 1002reflects light.

Note that the electrodes 9103 and 9105 in a liquid crystal element aredesirably formed at the same time. It is because when the electrodes9103 and 9105 in a liquid crystal element are formed at the same time,the process can be simplified, the number of masks (reticles) can bereduced, and cost can be reduced. However, it is not limited thereto andthe electrodes 9103 and 9105 in a liquid crystal element may beseparately formed. In such a case, it is possible that one of theelectrodes 9103 and 9105 in a liquid crystal element is transparent andthe other reflects light.

When the electrode serving as the pixel electrode (the electrode 9103 ina liquid crystal element) and the electrodes serving as the commonelectrodes (the electrodes 9305, 9104, and 9105 in a liquid crystalelement) are provided with the insulating layer therebetween, theoverlapped portion can serve as a capacitor. The capacitor can serve asa holding capacitor for holding an image signal.

As shown in FIGS. 78 and 79, when an electric potential difference isgenerated between the electrodes 9103 and 9305 in a liquid crystaldisplay, and between the electrodes 9103 and 9105 in a liquid crystalelement, liquid crystal molecules (9303 a and 9303 b) in a liquidcrystal layer 9303 rotate in a direction parallel to surfaces of theelectrodes 9103, 9305, and 9104 in a liquid crystal element (that is, ina plane parallel to the substrate). Therefore, an amount of light whichpasses the liquid crystal layer 9303 can be controlled. That is, apolarization state of light can be controlled and an amount of lightwhich passes a polarizing plate which is provided over an outer side ofthe substrate can be controlled. FIG. 79 corresponds to FIGS. 77A and112A. The liquid crystal molecules (9303 a and 9303 b) shown in FIG. 79rotate in a similar manner to liquid crystal molecules shown in FIGS.77A, 77B, 112A, and 112B. Light enters the liquid crystal display devicefrom outside and passes the liquid crystal layer 9303, passes theelectrode 9103 in a liquid crystal element and the insulating layers9204 and 9304, reflects off the electrode 9305 in a liquid crystalelement, passes the insulating layers 9204 and 9304 and the electrode9103 in a liquid crystal element, and exits from the liquid crystaldisplay device, in this order.

Note that an electrode 9004 in FIG. 79 corresponds to the electrodes9305 and 9104 in a liquid crystal element in FIG. 78. An insulatinglayer 9005 in FIG. 79 corresponds to the insulating layers 9204 and 9304in FIG. 78.

As shown in FIG. 79, since an electrode serving as a common electrode isprovided below an electrode serving as a pixel electrode, in a crosswisedirection, or in an oblique direction (including an upper obliquedirection and a lower oblique direction) of the electrode serving as apixel electrode, more electrical field component parallel to thesubstrate is generated, in regions 9002 and 9003. As a result, a viewingangle characteristic is further improved.

Note that since the insulating layers 9204 and 9304 hardly haverefractive index anisotropy, when light passes therethrough, thepolarization state does not change.

Note that in the portion which conducts display by reflecting light(reflective portion) 1001 and the portion which conducts display byhaving light pass therethrough (transmissive portion) 1002, a colorfilter is provided in a light path, thereby making light having adesired color. Light emitted from each pixel is mixed to display animage.

The color filter may be provided over a counter substrate which isprovided over the liquid crystal layer 9303 or over the electrode 9103in a liquid crystal element. Alternatively, the color filter may beprovided over the insulating layer 9304 or as a part thereof.

Note that a black matrix may be provided as well as the color filter.

Note that in the portion which conducts display by reflecting light(reflective portion) 1001, light passes the liquid crystal layer 9303twice. That is, external light enters the liquid crystal layer 9303 fromthe counter substrate side, reflects off the electrode 9305 in a liquidcrystal element, enters the liquid crystal layer 9303 again, and thenexits through the counter substrate side. In this manner, light passesthe liquid crystal layer 9303 twice.

On the other hand, in the portion which conducts display by having lightpass therethrough (transmissive portion) 1002, light passes theelectrode 9104 in a liquid crystal element, enters the liquid crystallayer 9303, and then exits through the counter substrate. That is, lightpasses the liquid crystal layer 9303 once.

The liquid crystal layer 9303 has refractive index anisotropy,therefore, a polarization state of light changes depending on thedistance traveled by the light in the liquid crystal layer 9303, whichleads to inaccurate image display. Therefore, the polarization state oflight needs to be adjusted. The thickness of the liquid crystal layer9303 (so-called cell gap) in the portion which conducts display byreflecting light (reflective portion) 1001 is thinned so that thedistance traveled by light in the liquid crystal layer 9303 can beprevented from being too long even when the light passes therethroughtwice.

Note that the insulating layers 9204 and 9304 hardly have refractiveindex anisotropy; therefore, a polarization state of light passingtherethrough does not change. Accordingly, presence and thickness of theinsulating layers 9204 and 9304 do not have much influence.

To make the thickness of the liquid crystal layer 9303 (so-called cellgap) thin, a film for adjusting the thickness thereof may be provided.In FIG. 78, the insulating layer 9204 corresponds to such a film. Thatis, in the portion which conducts display by reflecting light(reflective portion) 1001, the insulating layer 9204 is a layer providedfor adjusting the thickness of the liquid crystal layer. Providing theinsulating layer 9204 can make the liquid crystal layer in thereflective portion 1001 thinner than that in the transmissive portion1002.

Note that the thickness of the liquid crystal layer 9303 in thereflective portion 1001 is desirably half of that of the transmissiveportion 1002. Here, the half may include a deviation unrecognizable byhuman eyes.

Note that light is not always emitted in a direction perpendicular, thatis, in a direction normal to the substrate. Light is often emittedobliquely. Therefore, with all cases considered, the distance traveledby light needs to be approximately the same in the reflective portion1001 and the transmissive portion 1002. Therefore, the thickness of theliquid crystal layer 9303 in the reflective portion 1001 is desirablyapproximately one-third to two-thirds of that of the transmissiveportion 1002.

Thus, if a film for adjusting the thickness of the liquid crystal layer9303 is placed over the substrate side where the electrode 9103 in aliquid crystal element is provided, the formation thereof becomeseasier. That is, on the substrate side where the electrode 9103 in aliquid crystal element is provided, various wires, electrodes, and filmsare formed. The film for adjusting the thickness of the liquid crystallayer 9303 can be formed by using such wires, electrodes, and films;therefore, the film can be formed with few difficulties. Besides, a filmhaving another function can be formed in the same step, therefore, theprocess can be simplified and the cost can be reduced.

A liquid crystal display device of the present invention with theforegoing structure has a wide viewing angle and less color-shift due tothe angle at which its display screen is watched. In addition, a liquidcrystal display device of the present invention can provide an imagewhich is favorably recognized outdoors in the sun and dark indoors (oroutdoors at night).

Although the electrodes 9305 and 9104 in a liquid crystal element arearranged in the same plane in FIG. 78, it is not limited thereto. Theymay be formed in different planes.

Note that in FIG. 78 the electrodes 9305 and 9104 in a liquid crystalelement are arranged apart from each other. However, it is not limitedthereto. The electrodes 9305 and 9104 in a liquid crystal element may bearranged in contact with each other, or they may be formed of oneelectrode. Alternatively, the electrodes 9305 and 9104 in a liquidcrystal element may be electrically connected to each other. Inaddition, the electrodes 9105 and 9104 in a liquid crystal element maybe electrically connected to each other.

In FIG. 78, the insulating layer 9204 is placed as a film for adjustingthe thickness of the liquid crystal layer 9303. However, it is notlimited thereto and the film for adjusting the thickness of the liquidcrystal layer 9303 may be provided on the counter substrate side.

Although the film is provided to thin the liquid crystal layer 9303, thefilm may be removed in a predetermined portion so as to thicken theliquid crystal layer 9303.

The reflective electrode may have an even surface, but desirably has anuneven surface. With the uneven surface, it is possible to diffuse andreflect light. As a result, light can be scattered and luminance can beimproved.

Note that as shown in FIG. 80, in the transmissive portion 1002, theelectrode 9104 in a liquid crystal element is not necessarily provided.

In that case, as shown in FIG. 81, voltage is applied between theelectrodes 9105 and 9103 in a liquid crystal element to control theliquid crystal molecules (9303 a and 93036).

As described above, since the electrode 9104 in a liquid crystal elementis not provided in the transmissive portion 1002, the process can besimplified, the number of masks (reticles) can be reduced, and the costcan be reduced.

Embodiment Mode 2

An example of a liquid crystal display device of the present inventionhaving a structure different from that of Embodiment Mode 1 isdescribed. A portion having the same function as that of Embodiment Mode1 is denoted by the same reference numeral.

FIG. 82 shows an example of a liquid crystal display device which isdifferent from that shown in FIG. 78 in that the electrodes 9305 and9104 in a liquid crystal element are stacked. When the electrodes 9305and 9104 in a liquid crystal element are required to have the sameelectric potential, they may be stacked to be connected electrically toeach other.

Although the electrode 9104 in a liquid crystal element is placed belowthe electrode 9305 in a liquid crystal element, it is not limitedthereto. The electrode 9104 in a liquid crystal element may be placedover the electrode 9305 in a liquid crystal element.

Although the electrode 9104 in a liquid crystal element is placed in thewhole region below the electrode 9305 in a liquid crystal element, it isnot limited thereto. The electrode 9104 in a liquid crystal element maybe placed over and below a part of the electrode 9305 in a liquidcrystal element.

In a case where the electrode 9104 in a liquid crystal element is placedin the whole region below the electrode 9305 in a liquid crystalelement, both the electrodes 9305 and 9104 in a liquid crystal elementcan be formed using one mask. In general, the electrodes 9305 and 9104in a liquid crystal element are each formed using different masks.However, in this case, a mask such as a halftone or graytone is used andby changing thickness of a resist by region, the electrodes 9305 and9104 in a liquid crystal element can be formed with one mask. As aresult, the process can be simplified, the number of steps can bereduced, and the number of masks (the number of reticles) can bereduced, so that the cost can be reduced.

In FIG. 83, a liquid crystal display device is shown in which theelectrodes 9305 and 9104 in a liquid crystal element are electricallyconnected by being partially overlapped with each other. The electrodes9305 and 9104 in a liquid crystal element may be electrically connectedin such a structure.

Although the electrode 9104 in a liquid crystal element is placed overelectrode 9305 in a liquid crystal element to be in contact with eachother, it is not limited thereto. The electrode 9305 in a liquid crystalelement may be placed over the electrode 9104 in a liquid crystalelement to be in contact with each other.

In this manner, by not arranging the electrode 9104 in a liquid crystalelement in a wide region over the electrode 9305 in a liquid crystalelement, loss of light therein can be reduced.

In FIG. 84, the electrodes 9305 and 9104 in a liquid crystal element areprovided in different layers with an insulating layer 9306 therebetween.As in FIG. 85, the electrodes 9305 and 9104 in a liquid crystal elementmay be provided in different layers.

When the electrodes 9305 and 9104 in a liquid crystal element are formedin different layers, the distance between the electrodes 9305 and 9104in a liquid crystal element in the reflective portion 1001 isapproximately the same as that in the transmissive portion 1002.Therefore, the gap between the electrodes in the reflective portion 1001and that in the transmissive portion 1002 can be approximately the same.Since application and intensity of electrical filed change according tothe gap between electrodes, when the gaps between the electrodes areapproximately the same in the reflective portion 1001 and thetransmissive portion 1002, approximately the same level of electricalfields can be applied thereto. Therefore, liquid crystal molecules canbe controlled with accuracy. In addition, since the liquid crystalmolecules rotate in approximately the same manner in the reflectiveportion 1001 and the transmissive portion 1002, an image withapproximately the same gray-scale can be viewed whether the image isdisplayed or viewed by the liquid crystal display device used as atransmissive type or as a reflective type.

Although the electrode 9104 in a liquid crystal element is placed in thewhole region below the electrode 9305 in a liquid crystal element, it isnot limited thereto. The electrode 9104 in a liquid crystal elementneeds to be provided at least in the transmissive portion 1002.

Note that a contact hole may be formed in the insulating layer 9306 toconnect the electrodes 9104 and 9305 in a liquid crystal element.

FIG. 85 shows an example of a liquid crystal display device which isdifferent from that shown in FIG. 84 in that the electrode 9305 in aliquid crystal element is provided in a layer lower than the electrode9104 (a layer further away from the liquid crystal layer 9303) in aliquid crystal element.

Although the electrode 9104 in a liquid crystal element is also formedin the reflective portion 1001, it is not limited thereto. The electrode9104 in a liquid crystal element needs to be provided at least in thetransmissive portion 1002.

Note that in the case where the electrode 9104 in a liquid crystalelement is also formed in the reflective portion 1001, the liquidcrystal layer 9303 is controlled according to the voltage between theelectrodes 9104 and 9103 in a liquid crystal element. In that case, theelectrode 9305 in a liquid crystal element serves only as the reflectiveelectrode and the electrode 9104 in a liquid crystal element serves asthe common electrode in the reflective portion 1001.

Therefore, in that case, voltage supplied to the electrode 9305 in aliquid crystal element is arbitrary. The same voltage as the electrode9104 in a liquid crystal element or the electrode 9103 in a liquidcrystal element may be supplied to the electrode 9305 in a liquidcrystal element. In that case, a capacitor is formed between theelectrodes 9305 and 9104 in a liquid crystal element, which may serve asa holding capacitor for holding an image signal.

Note that a contact hole may be formed in the insulating layer 9306 toconnect the electrodes 9104 and 9305 in a liquid crystal element to eachother.

In FIG. 86, the electrode 9305 in a liquid crystal element in thereflective portion 1001 and the electrodes 9103 and 9105 in a liquidcrystal element in the transmissive portion 1002 are formed over theinsulating layer 9304. In addition, the insulating layer 9204 is formedover the electrode 9305 in a liquid crystal element and the electrodes9103 and 9105 in a liquid crystal element in the reflective portion areformed thereover. The electrode 9104 in a liquid crystal element isformed below the insulating layer 9304.

Although the electrode 9104 in a liquid crystal element is also formedin the reflective portion 1001, it is not limited thereto. The electrode9104 in a liquid crystal element needs to be provided at least in thetransmissive portion 1002.

Note that a contact hole may be formed in the insulating layer 9304 toconnect the electrodes 9104 and 9305 in a liquid crystal element to eachother.

Note that as shown in FIG. 93, the electrode 9104 in a liquid crystalelement is not necessarily provided in the transmissive portion 1002.

In such a case, as shown in FIG. 81, voltage is applied between theelectrodes 9105 and 9103 in a liquid crystal element to control theliquid crystal molecules (9303 a and 9303 b).

As described above, since the electrode 9104 in a liquid crystal elementis not provided in the transmissive portion 1002, the process can besimplified, the number of masks (reticles) can be reduced, and the costcan be reduced.

Note that in FIGS. 78 to 86 and 93, although unevenness of surfaces ofthe electrodes are not shown, the surfaces of the electrodes 9103, 9305,9104, and 9105 in a liquid crystal element are not limited to be flat.Their surfaces may be uneven.

Note that in FIGS. 78 to 86 and 93, although unevenness of surfaces ofthe insulating layers 9204, 9304, and 9306 are not shown, the surfacesof the insulating layers 9204, 9304, and 9306 are not limited to beflat. Their surfaces may be uneven.

Note that by making the surface of the reflective electrode be veryuneven, light can be diffused. As a result, luminance of the displaydevice can be improved. Therefore, the reflective electrode and thetransparent electrode (the electrodes 9305 and 9104 in a liquid crystalelement) shown in FIGS. 78 to 86 and 93 may have uneven surfaces.

Note that the uneven surface preferably has a shape with which light canbe diffused as easily as possible.

In the transmissive portion 1002, the transparent electrode desirablydoes not have unevenness so as not to affect application of anelectrical field. Note that even if there is unevenness, there is noproblem if display is not affected.

FIG. 87 shows a case where the surface of the reflective electrode inFIG. 78 is uneven. Each of FIGS. 88 and 89 shows a case where thesurface of the reflective electrode in FIG. 82 is uneven. FIG. 90 showsa case where the surface of the reflective electrode in FIG. 83 isuneven. FIG. 91 shows a case where the surface of the reflectiveelectrode in FIG. 84 is uneven. FIG. 92 shows a case where the surfaceof the reflective electrode in FIG. 85 is uneven.

The description of FIGS. 78 to 86 and 93 where the surface of thereflective electrode is not uneven can be applied to FIGS. 86 to 92.

FIG. 87 shows an example of a liquid crystal display device which isdifferent from that shown in FIG. 78 in that a convex-shaped scatterer9307 is provided below the electrode 9305 in a liquid crystal element.By providing the convex-shaped scatterer, the electrode 9305 in a liquidcrystal element has an uneven surface, and light is scattered anddegradation of contrast and glare due to reflection of light can beprevented; thereby improving luminance.

Note that the shape of the scatterer 9307 desirably has a shape withwhich light is diffused as easily as possible. However, since anelectrode and a wire may be formed thereover, a smooth shape isdesirable so as to prevent breaking of the electrodes and wires.

FIG. 89 shows an example of a liquid crystal display device which isdifferent from that shown in FIG. 88 in that the electrodes 9305 and9104 in a liquid crystal element are stacked.

Since the electrodes 9104 and 9305 in a liquid crystal element sticktogether in a large area, contact resistance can be reduced.

FIG. 90 shows an example of a liquid crystal display device which isdifferent from that shown in FIG. 89 in that a scatterer 9203 isprovided between the electrodes 9305 and 9104 in a liquid crystalelement.

Since the scatterer 9203 is formed after forming the electrode 9104 in aliquid crystal element, the electrode 9104 in a liquid crystal elementcan be flattened in the reflective portion 1001.

FIG. 90 shows an example of a liquid crystal display device which isdifferent from that shown in FIG. 83 in that the convex-shaped scatterer9203 is provided below the electrode 9305 in a liquid crystal element.

FIG. 91 shows an example of a liquid crystal display device which isdifferent from that shown in FIG. 84 in that the surface of theinsulating layer 9306 is partially uneven. The surface of the electrode9305 in a liquid crystal element becomes uneven, reflecting such theshape of the insulating layer 9306.

FIG. 92 shows an example of a liquid crystal display device which isdifferent from that shown in FIG. 85 in that the surface of theelectrode 9305 in a liquid crystal element becomes uneven by providingan insulating layer 9308 having a partially uneven surface below theelectrode 9305 in a liquid crystal element.

Although in FIGS. 78 to 93, the film for adjusting the thickness of theliquid crystal layer 9303 is formed below the electrode 9103 in a liquidcrystal element, it is not limited thereto. As shown in FIG. 94, theinsulating layer 9204 for adjusting the thickness of the liquid crystallayer 9303 may be placed over the electrodes 9103 and 9105 in a liquidcrystal element.

In that case, as shown in FIG. 95, the electrode 9104 in a liquidcrystal element is not necessarily provided in the transmissive portion1002.

In such a case, as shown in FIG. 81, voltage is applied between theelectrodes 9105 and 9103 in a liquid crystal element to control theliquid crystal molecules (9303 a and 9303 b).

As described above, since the electrode 9104 in a liquid crystal elementis not provided in the transmissive portion 1002, the process can besimplified, the number of masks (reticles) can be reduced, and the costcan be reduced.

FIG. 94 corresponds to FIG. 78. In FIGS. 82 to 92, as in the case ofFIG. 94, the insulating layer 9204 for adjusting the thickness of theliquid crystal layer 9303 can be placed over the electrode 9103 in aliquid crystal element.

Although in many drawings in FIGS. 78 to 94, the film for adjusting thethickness of the liquid crystal layer 9303 is provided on the substrateside where the electrode 9103 in a liquid crystal element is formed, itis not limited thereto. The film for adjusting the thickness of theliquid crystal layer 9303 may be placed over a counter substrate side.

By placing the film for adjusting the thickness of the liquid crystallayer 9303 on the counter substrate side, the electrode 9103 in a liquidcrystal element can be arranged in the same plane in the reflectiveportion 1001 and that in the transmissive portion 1002. Therefore, thedistances between the electrodes in the reflective portion 1001 and thetransmissive portion 1002 can be approximately the same. Sinceapplication and intensity of electrical filed change according to adistance between electrodes, when the gaps between the electrodes areapproximately the same in the reflective portion 1001 and thetransmissive portion 1002, approximately the same level of electricalfields can be applied thereto. Therefore, liquid crystal molecules canbe controlled with accuracy. In addition since the liquid crystalmolecules rotate in approximately the same manner in the reflectiveportion 1001 and the transmissive portion 1002, an image withapproximately the same gray-scale can be viewed whether the image isdisplayed or viewed by the liquid crystal display device used as atransmissive type or as a reflective type.

When the film for adjusting the thickness of the liquid crystal layer9303 is provided, there is a possibility that an alignment state of theliquid crystal molecules becomes disordered and a defect such asdisclination may be caused. However, placement of the film for adjustingthe thickness of the liquid crystal layer 9303 over a counter substrate9202 can set the counter substrate 9202 apart from the electrode 9103 ina liquid crystal element and therefore, an electrical field applied tothe liquid crystal layer is not weakened, the alignment state of theliquid crystal molecules is hardly disordered, and an image can beprevented from being hardly recognizable.

Note that the number of steps for forming the counter substrate is smallsince only the color filter, the black matrix, and the like are providedthereto. Therefore, even if the film for adjusting the thickness of theliquid crystal layer 9303 is provided to the counter substrate 9202, ayield is not easily reduced. Even if a defect is generated, since thenumber of steps is small and the cost is low, waste of the manufacturingcost can be suppressed.

Note that in a case where the film for adjusting the thickness of theliquid crystal layer 9303 is provided to the counter substrate 9202,particles serving as a scattering material may be contained in the filmfor adjusting the thickness of the liquid crystal layer 9303 so thatlight is diffused and luminance is improved. The particles are formed ofa transparent resin material which has a refractive index different froma base material (such as an acrylic resin) forming a film for adjustinga gap. When the particles are contained, light can be scattered andcontrast and luminance of a displayed image can be improved.

FIG. 96 shows a case where the film for adjusting the thickness of theliquid crystal layer is provided to the counter substrate in FIG. 78.FIG. 97 shows a case where the film for adjusting the thickness of theliquid crystal layer is provided to the counter substrate in FIG. 82.FIG. 98 shows a case where the film for adjusting the thickness of theliquid crystal layer is provided to the counter substrate in FIG. 83.FIG. 99 shows a case where the film for adjusting the thickness of theliquid crystal layer is provided to the counter substrate in FIG. 84.FIG. 100 shows a case where the film for adjusting the thickness of theliquid crystal layer is provided to the counter substrate in FIG. 85.FIG. 101 shows a case where the film for adjusting the thickness of theliquid crystal layer is provided to the counter substrate in FIG. 80.

Therefore, the description on FIGS. 78 to 86 can be applied to FIGS. 96to 101.

FIG. 96 shows an example of a liquid crystal display device which isdifferent from that shown in FIG. 78 in that an insulating layer 9201for adjusting the thickness of the liquid crystal layer 9303 is providedon another side of the liquid crystal layer 9303 than a side of whichthe electrode 9103 in a liquid crystal element is provided, and theelectrode 9103 in a liquid crystal element is provided over theinsulating layer 9304.

FIG. 97 shows an example of a liquid crystal display device which isdifferent from that shown in FIG. 82 in that the insulating layer 9201for adjusting the thickness of the liquid crystal layer 9303 is providedon another side of the liquid crystal layer 9303 than a side of whichthe electrode 9103 in a liquid crystal element is provided, and theelectrode 9103 in a liquid crystal element is formed over the insulatinglayer 9304.

FIG. 98 shows an example of a liquid crystal display device which isdifferent from that shown in FIG. 83 in that the insulating layer 9201for adjusting the thickness of the liquid crystal layer 9303 is providedon another side of the liquid crystal layer 9303 than a side of whichthe electrode 9103 in a liquid crystal element is provided, and theelectrode 9103 in a liquid crystal element is formed over the insulatinglayer 9304.

FIG. 99 shows an example of a liquid crystal display device which isdifferent from that shown in FIG. 84 in that the insulating layer 9201for adjusting the thickness of the liquid crystal layer 9303 is providedon another side of the liquid crystal layer 9303 than a side of whichthe electrode 9103 in a liquid crystal element is provided, and theelectrode 9103 in a liquid crystal element is formed over the insulatinglayer 9304.

FIG. 100 shows an example of a liquid crystal display device which isdifferent from that shown in FIG. 87 in that the insulating layer 9201for adjusting the thickness of the liquid crystal layer 9303 is providedon another side of the liquid crystal layer 9303 than a side of whichthe electrode 9103 in a liquid crystal element is provided, and theelectrode 9103 in a liquid crystal element is formed over the insulatinglayer 9304.

FIG. 101 shows an example of a liquid crystal display device which isdifferent from that shown in FIG. 80 in that the insulating layer 9201for adjusting the thickness of the liquid crystal layer 9303 is providedon another side of the liquid crystal layer 9303 than a side of whichthe electrode 9103 in a liquid crystal element is provided, and theelectrode 9103 in a liquid crystal element is formed over the insulatinglayer 9304.

Note that in FIGS. 96 to 101, although unevenness of surfaces of theelectrodes are not shown, the surfaces of the electrodes 9103, 9305,9104, and 9105 in a liquid crystal element are not limited to be flat.Their surfaces may be uneven.

Note that in FIGS. 96 to 101, although unevenness of surfaces of theinsulating layers 9204, 9304, and 9306 are not shown, the surfaces ofthe insulating layers 9204, 9304, and 9306 are not limited to be flat.Their surfaces may be uneven.

Note that by making the surface of the reflective electrode be veryuneven, light can be diffused. As a result, luminance of the displaydevice can be improved. Therefore, the reflective electrode and thetransparent electrode (the electrode 9305 in a liquid crystal elementand the electrode 9104 in a liquid crystal element) shown in FIGS. 96 to101 may have uneven surfaces.

Note that the uneven surface preferably has a shape with which light canbe diffused as easily as possible.

In the transmissive portion 1002, the transparent electrode desirablydoes not have unevenness so as not to affect application of anelectrical field to the liquid crystal layer. Note that even if there isunevenness, there is no problem if display is not affected.

Note that as in the case of FIGS. 78 to 86, in which the reflectiveelectrode may have an uneven surface as shown in FIGS. 87 to 92, thereflective electrode in FIGS. 96 to 101 may have an uneven surface. FIG.102 shows a case where the reflective electrode in FIG. 96 hasunevenness. Similarly, the reflective electrode in FIGS. 97 to 101 mayhave unevenness.

The description of FIG. 96 where the surface of the reflective electrodeis not uneven can be applied to FIG. 102.

FIG. 102 shows an example of a liquid crystal display device which isdifferent from that shown in FIG. 96 in that the insulating layer 9201for adjusting the thickness of the liquid crystal layer 9303 is providedon another side of the liquid crystal layer 9303 than a side of whichthe electrode 9103 in a liquid crystal element is provided, and theelectrode 9103 in a liquid crystal element is formed over the insulatinglayer 9304.

In FIGS. 78 to 102, there are cases where the film for adjusting thethickness of the liquid crystal layer 9303 is placed on the substrateside where the electrode 9103 in a liquid crystal element is provided orthe counter substrate side, but it is not limited thereto. The film foradjusting the thickness of the liquid crystal layer 9303 itself is notnecessarily formed, as shown in FIG. 103. FIG. 103 corresponds to FIGS.78 and 96. Besides in the cases shown in FIGS. 78 and 96, the film foradjusting the thickness of the liquid crystal layer 9303 itself is notnecessarily formed in the cases shown in FIGS. 79 to 95 and 97 to 102.

When the film for adjusting the thickness of the liquid crystal layer9303 itself is not provided, a distance traveled by light in the liquidcrystal layer in the reflective portion is different from that in thetransmissive portion. Therefore, it is desirable to provide, forexample, a retardation film (such as a quarter-wave plate) or a materialwith refractive index anisotropy (such as liquid crystal) in a lightpath so as to change a polarization state of light. For example, if aretardation film is provided between the counter substrate and thepolarizing plate on the side of the counter substrate on which theliquid crystal layer is not provided, the light transmission state canbe the same in the reflective portion and the transmissive portion.

Although the electrodes 9103 in a liquid crystal element may be formedin the same plane in the transmissive portion 1002 in FIGS. 78 to 103and the foregoing description, it is not limited thereto. The 9103electrodes in a liquid crystal element may be formed on differentplanes.

Although the electrodes 9105 in a liquid crystal element may be formedin the same plane in the transmissive portion 1002 in FIGS. 78 to 103and the foregoing description, it is not limited thereto. The electrodes9105 in a liquid crystal element may be formed on different planes.

Although the electrodes 9103 in a liquid crystal element may be formedin the same plane in the reflective portion 1001, in FIGS. 78 to 103 andthe foregoing description it is not limited thereto. The electrodes 9103in a liquid crystal element may be formed on different planes.

Although the electrodes 9105 in a liquid crystal element may be formedin the same plane in the reflective portion 1001, in FIGS. 78 to 103 andthe foregoing description it is not limited thereto. The electrodes 9105in a liquid crystal element may be formed on different planes.

Although the electrodes 9305 and 9104 in a liquid crystal element in thereflective portion 1001 may be formed to be plain-shaped in FIGS. 78 to103 and the foregoing description, it is not limited thereto. Theelectrodes 9305 and 9104 in a liquid crystal element may be formed tohave a comb-shape, a slit, or an aperture.

Although the electrode 9104 in a liquid crystal element in thetransmissive portion 1002 may be formed to be plain-shaped in FIGS. 78to 103 and the foregoing description, it is not limited thereto. Theelectrode 9104 in a liquid crystal element may be formed to have acomb-shape, a slit, or an aperture.

Although the electrodes 9305 and 9104 in a liquid crystal element may beformed below the electrode 9103 in a liquid crystal element in thereflective portion 1001 in FIGS. 79 to 104 and the foregoingdescription, it is not limited thereto. If the electrodes 9305 and 9104in a liquid crystal have a comb-shape, a slit, or an aperture, they maybe formed in the same level as the electrode 9103 in a liquid crystalelement or over the electrode 9103 in a liquid crystal element.

Although the electrodes 9305 and 9104 in a liquid crystal element may beformed below the electrode 9105 in a liquid crystal element in thereflective portion 1001 in FIGS. 78 to 103 and the foregoingdescription, it is not limited thereto. If the electrodes 9305 and 9104in a liquid crystal element have a comb-shape, a slit, or an aperture,they may be formed in the same level as the electrode 9105 in a liquidcrystal element or over the electrode 9105 in a liquid crystal element.

Although the electrodes 9305 and 9104 in a liquid crystal element may beformed below the electrode 9103 in a liquid crystal element in thetransmissive portion 1002 in FIGS. 78 to 103 and the foregoingdescription, it is not limited thereto. If the electrodes 9305 and 9104in a liquid crystal element have a comb-shape, a slit, or an aperture,they may be formed in the same level as the electrode 9103 in a liquidcrystal element or over the electrode 9103 in a liquid crystal element.

Although the electrodes 9305 and 9104 in a liquid crystal element may beformed below the electrode 9105 in a liquid crystal element in thetransmissive portion 1002 in FIGS. 78 to 103 and the foregoingdescription, it is not limited thereto. If the electrodes 9305 and 9104in a liquid crystal element have a comb-shape, a slit, or an aperture,they may be formed in the same level as the electrode 9105 in a liquidcrystal element or over the electrode 9105 in a liquid crystal element.

Note that in the foregoing structure such as structures shown in FIGS.78 to 103 and combination thereof, a color filter may be provided overthe counter substrate which is provided over the liquid crystal layer9303 or may be provided over the substrate over which the electrode 9103in a liquid crystal element is provided.

For example, a color filter may be provided in the insulating layers9304, 9204, 9306, and 9308 or as a part thereof.

Note that a black matrix may be provided in a similar manner to a colorfilter. Needless to say, both a color filter and a black matrix may beprovided.

Thus, if the insulating layer serves as the color filter or the blackmatrix, a material cost can be reduced.

When the color filter or the black matrix is placed over the substrateover which the electrode 9103 in a liquid crystal element is provided, amargin of arrangement of the counter substrate is enhanced.

Note that a variety of positions, kinds, and shapes of the electrode ina liquid crystal element, and positions and shapes of the insulatinglayer can be employed. That is, a position of the electrode in a liquidcrystal element in one drawing and a position of the insulating layer inanother drawing can be combined so as to make many variations. Forexample, the example shown in FIG. 88 is formed by changing the shape ofthe electrode 9305 in a liquid crystal element in FIG. 79 to have anuneven shape. For another example, the position and the shape of theelectrode 9104 in a liquid crystal element in FIG. 79 are changed, sothat the example shown in FIG. 87 is formed. In the foregoing drawings,each part in each drawing can be combined with the corresponding part inanother drawing; therefore, enormous numbers of variations can beformed.

Embodiment Mode 3

In Embodiment Modes 1 and 2, a description is made of a case where thereflective portion and the transmissive portion are provided, that is,the case where a semi transmissive liquid crystal display device isprovided, but it is not limited thereto.

When one of the electrodes 9305 and 9104 in a liquid crystal element isremoved and the other is provided over the whole surface, a reflectiveor a transmissive liquid crystal display device can be formed.

When the electrode 9305 in a liquid crystal element is removed and theelectrode 9104 in a liquid crystal element is provided over the wholesurface, a transmissive liquid crystal element is formed. When thetransmissive liquid crystal display device is used indoors, bright andbeautiful display can be conducted since an aperture ratio thereof ishigh.

When the electrode 9104 in a liquid crystal element is removed and theelectrode 9305 in a liquid crystal element is provided over the wholesurface, a reflective liquid crystal display device is formed. When thereflective liquid crystal display device is used outdoors, clear displaycan be conducted since reflectance thereof is high; therefore, a displaydevice with low power consumption can be realized. When the reflectiveliquid crystal display device is used indoors, display can be conductedby providing a front light over a display portion.

When the liquid crystal display device is used as a reflective liquidcrystal display device or transmissive liquid crystal display device, adistance traveled by light does not vary in one pixel. Therefore, theinsulating layer 9204 for adjusting the thickness of the liquid crystallayer (cell gap) is not required.

FIG. 104 shows an example where the liquid crystal display device shownin FIG. 78 is transmissive. FIG. 105 shows an example where the liquidcrystal display device shown in FIG. 87 is reflective.

As shown in FIGS. 104 and 105, a contact hole may be formed in theinsulating layer 9304 so that the electrodes 9305, 9104, and 9105 in aliquid crystal element are connected. Since those electrodes serve asthe common electrodes, they are desirably connected electrically.

Note that the drawings and descriptions on FIGS. 77 to 103 can beapplied to a transmissive or reflective liquid crystal display device,in a similar manner to FIGS. 104 and 105.

Note that the description in Embodiment Modes 1 and 2 can be applied toor combined with this embodiment mode.

Embodiment Mode 4

An example of an active matrix liquid crystal display device of thepresent invention is described.

In this embodiment mode, an example is described, where a structuredescribed in Embodiment Modes 1 to 3 or a structure realized bycombination of portions shown in the drawings therein is formed with atransistor.

Note that in the present invention, a transistor is not always required;therefore, the present invention can be applied to a display devicewithout a transistor, that is, a so-called passive matrix displaydevice.

In this embodiment mode, a case is described where a liquid crystaldisplay device is transmissive and is controlled using a top gatetransistor.

However, it is not limited thereto, and a bottom gate transistor may beused.

FIG. 1 shows a liquid crystal display device including a substrate 100having an insulating surface (hereinafter referred to as an insulatingsubstrate), over which a thin film transistor 102, a first electrode103, a second electrode 104, and a third electrode 105 connected to thethin film transistor are formed. The first electrode 103 serves as apixel electrode. The second electrode 104 serves as a common electrode.The third electrode 105 serves as a common electrode.

Note that a gate electrode is a part of a gate line. A portion of thegate line which serves as an electrode for switching the thin filmtransistor 102 is the gate electrode.

A common wire is a wire electrically connected to electrodes provided ina liquid crystal element and which is led so that electrodes in a liquidcrystal element in a plurality of pixels provided in a liquid crystaldisplay device have the same electric potential. The electrode in aliquid crystal element electrically connected to the common wire iscalled a common electrode in general. On the other hand, an electrode ina liquid crystal element whose electric potential changes as neededaccording to electric potential from a source line is called a pixelelectrode in general.

The thin film transistor 102 is preferably formed over the insulatingsubstrate 100 with a base layer 101 therebetween. By providing the baselayer 101, entry of impurity elements from the insulating substrate 100to the thin film transistor 102, especially to a semiconductor layer canbe prevented. Silicon oxide, silicon nitride, or a stacked layer thereofcan be used for the base layer 101. Silicon nitride is preferablebecause it can prevent the entry of the impurity effectively. On theother hand, silicon oxide is preferable because it does not causetrapping of electric charge or hysteresis of electric characteristicseven if it is in contact with the semiconductor layer directly.

Although the thin film transistor 102 is a top gate type, it is notlimited thereto. The thin film transistor 102 may be a bottom gate type.

The thin film transistor 102 includes the semiconductor layer 111processed into a predetermined shape, a gate insulating layer 112covering the semiconductor layer or provided over the semiconductorlayer, a gate electrode 113 provided over the semiconductor layer withthe gate insulating layer therebetween, and source and drain electrodes116.

The gate insulating layer formed covering the semiconductor layer canprevent attachment or entry of an impurity to the semiconductor layereven if the semiconductor layer is exposed to atmosphere in a process.In addition, the gate insulating layer provided over the semiconductorlayer can be processed using the gate electrode as a mask; therefore,the number of masks can be reduced. Thus, a shape of the gate insulatinglayer 112 can be decided according to the process or the like, and itmay be that the gate insulating layer 112 is only formed below the gateelectrode or may be formed over the whole surface. Alternatively, thegate insulating layer 112 may be provided so as to be thick below or ina vicinity of the gate electrode and be thin in another region.

In the semiconductor layer, an impurity region 114 is provided. The thinfilm transistor becomes an N-type or a P-type depending on conductivityof the impurity region. The impurity region can be formed by adding theimpurity elements in a self-aligned manner using the gate electrode 113as a mask. Note that another mask may be prepared and used.

In the impurity region, its concentration can be varied. For example, alow-concentration impurity region and a high-concentration impurityregion can be provided. The low-concentration impurity region can beformed by making the gate electrode 113 have a tapered shape and byadding an impurity element in a self-aligned manner using such a gateelectrode. Alternatively, the low-concentration impurity region can beformed by varying the thickness of the gate insulating layer 112 ormaking the gate electrode have a tapered shape. In addition, theconcentration of the impurity region can be varied by forming a sidewallstructure in the side surfaces of the gate electrode 113. A structure inwhich a low-concentration impurity region and a high-concentrationimpurity region are provided is called an LDD (Lightly Doped Drain)structure. A structure where low-concentration impurity region and agate electrode are overlapped is called a GOLD (Gate-drain OverlappedLDD) structure. In such a thin film transistor including alow-concentration impurity region, short-channel effect which isgenerated as a gate length is shortened can be prevented. In addition,off-current can be reduced and concentration of an electrical field inthe drain region can be suppressed; thereby improving reliability of thetransistor.

The insulating layer 106 is provided to cover the semiconductor layer111 and the gate electrode 113. The insulating layer 106 can have asingle-layer structure or a stacked-layer structure. An inorganicmaterial or an organic material can be used for the insulating layer106. As an inorganic material, silicon oxide or silicon nitride can beused. As an organic material, polyimide, acrylic, polyamide, polyimideamide, a resist, benzocyclobutene, siloxane, or polysilazane can beused. Siloxane includes a skeleton structure formed by a bond of silicon(Si) and oxygen (O). An organic group containing at least hydrogen (suchas an alkyl group or aromatic hydrocarbon) is used as a substituent.Alternatively, a fluoro group may be used as the substituent. Furtheralternatively, a fluoro group and an organic group including at leasthydrogen may be used as the substituent. Note that polysilazane isformed using a polymer material having a bond of silicon (Si) andnitrogen (N) as a starting material. It is preferable to use an organicmaterial for the insulating layer 106 since flatness of the surfacethereof can be improved. When an inorganic material is used for theinsulating layer 106, the surface thereof follows the shapes of thesemiconductor layer or the gate electrode. In this case, the insulatinglayer 106 can be flat by being thickened.

An opening is formed in the insulating layer 106 to expose the impurityregion. A conductive layer is formed in the opening to form source anddrain electrodes 116. The conductive layer for the source and drainelectrodes is formed of an element selected from tantalum (Ta), tungsten(W), titanium (Ti), molybdenum (Mo), aluminium (Al), chromium (Cr),silver (Ag), copper (Cu), neodymium (Nd), or the like; an alloy materialcontaining the element as a main component; or a conductive materialsuch as metal nitride such as titanium nitride, tantalum nitride, ormolybdenum nitride. The conductive layer can have a single-layerstructure or a stacked-layer structure of those materials. Thestacked-layer structure can reduce resistance thereof. Another electrode117 or the like can be formed using the same conductive layer as thesource and drain electrode.

An insulating layer 107 is formed covering the source and drainelectrodes 116. The insulating layer 107 can be formed in a similarmanner to the insulating layer 106. That is, if the insulating layer 107is formed using an organic material, flatness thereof can be improved.Since the first electrode 103 and the third electrode 105 are formedover the insulating layer 107, it is desirable that flatness of theinsulating layer 107 be high. The first electrode 103 and the thirdelectrode 105 are provided for applying voltage to a liquid crystalmaterial, and they need to be flat; therefore, the flatness of theinsulating layer 107 is desirably high.

The first electrode 103 and the third electrode 105 are processed into acomb-shaped or processed to have a slit. The first electrode 103 and thethird electrode 105 are alternately arranged. In other words, the firstelectrode 103 and the third electrode 105 may be processed so as to beable to be alternately arranged. A gap between the first electrode 103and the third electrode 105 is 2 to 8 μm, preferably, 3 to 4 μm.Application of voltage to thus arranged first electrode 103 and thirdelectrode 105 generates an electrical field therebetween. Accordingly,orientation of the liquid crystal material can be controlled. Thusgenerated electrical field has many components parallel to thesubstrate. Therefore, a liquid crystal molecule rotates in a planeapproximately parallel to the substrate. Thus, transmission of light canbe controlled.

The first electrode 103 and the third electrode 105 formed over theinsulating layer 107 are formed of a conductive martial such as anelement selected from tantalum (Ta), tungsten (W), titanium (Ti),molybdenum (Mo), aluminium (Al), chromium (Cr), silver (Ag), or thelike; or an alloy material containing the element as a main component.When the first electrode 103 and the third electrode 105 need to betransparent, a transparent conductive material such as indium tin oxide(ITO), indium zinc oxide (IZO), indium tin oxide containing siliconoxide (ITSO), zinc oxide (ZnO), or silicon (Si) containing phosphorus orboron can be used.

Then, the second electrode 104 is described. The second electrode 104 isprovided over the base layer 101 or the gate insulating layer 112. Thesecond electrode 104 is formed over one pixel region. Specifically, thesecond electrode 104 is formed over one pixel region except a thin filmtransistor forming region. In other words, unlike the comb-shaped thirdelectrode 105, the second electrode 104 is provided over one pixelregion, in other words, a region below the comb-shaped third electrode105 and the first electrode 103. That is, the second electrode 104 isprovided to be plain-shaped. The second electrode 104 is formed over onepixel region and the shape thereof is not limited. For example, thesecond electrode 104 may be formed over the whole surface of one pixelregion, or may be formed over one pixel region to be comb-shaped or mayinclude a slit or hole.

The second electrode 104 is formed of a conductive martial such astantalum (Ta), tungsten (W), titanium (Ti), molybdenum (Mo), aluminium(Al), chromium (Cr), silver (Ag), indium tin oxide (ITO), indium zincoxide (IZO), indium tin oxide containing silicon oxide (ITSO), zincoxide (ZnO), or silicon (Si) containing phosphorus or boron. The secondelectrode 104 can be formed in the same layer as the semiconductor layer111; therefore the semiconductor layer may be used for the secondelectrode 104. However, note that since the second electrode 104 needsto be conductive, a crystallized semiconductor layer, a semiconductorlayer doped with an impurity element, or crystallized semiconductorlayer doped with an impurity element is used.

In that case, the semiconductor layer in the thin film transistor 102and the second electrode 104 formed by the semiconductor layer aredesirably formed at the same time. As a result, the process can besimplified and the cost can be reduced.

The second electrode 104 is electrically connected to the thirdelectrode 105 with the electrode 117 therebetween.

When a transmissive liquid crystal display device is formed, the secondelectrode 104 and the third electrode 105 are formed of a transparentconductive material such as indium tin oxide (ITO), indium zinc oxide(IZO), indium tin oxide containing silicon oxide (ITSO), zinc oxide(ZnO), or silicon (Si) containing phosphorus or boron. Those transparentmaterials have high resistance compared with another conductive materialsuch as Al. Therefore, the electrode 117 formed of a conductive materialwith low resistance such as tantalum (Ta), tungsten (W), titanium (Ti),molybdenum (Mo), aluminium (Al), chromium (Cr), or silver (Ag); or awire formed at the same time as the gate electrode 113 can be used forconnecting the second electrode 104 and the third electrode 105, wherebythe electrode 117 and the wire can serve as an auxiliary electrode orauxiliary wire of the second electrode 104 and the third electrode 105.As a result, uniform voltage can be applied to the second electrode 104and the third electrode 105, which means that voltage drop caused byresistance of the electrodes can be prevented in the second electrode104 and the third electrode 105.

At this time, it is desirable to use a conductive layer formed at thesame time as the gate electrode 113 as the auxiliary wire. In that case,the auxiliary wire is desirably placed so as to be approximatelyparallel to the gate wire, whereby an efficient layout can be achieved.

When voltage is applied to such second electrode 104 and the comb-shapedfirst electrode 103, an electrical field is also generated therebetween.That is, electrical fields generate between the second electrode 104 andthe first electrode 103 and between the comb-shaped third electrode 105and the first electrode 103. Tilting and rotation angle of the liquidcrystal material are controlled according to the electrical fieldbetween the two pair of electrodes, whereby the gray-scale display canbe conducted. As a result, in a part of the liquid crystal material,whose tilting has not been sufficiently controlled by an electricalfield generated by one pair of electrodes of the comb-shaped thirdelectrode 105 and the comb-shaped first electrode 103, tilting of theliquid crystal material can be sufficiently controlled by electricalfields generated by two pairs of electrodes. Specifically, by providingthe second electrode 104, the tilting of the liquid crystal materialright above the comb-shaped third electrode 105 or comb-shaped firstelectrode 103 can be sufficiently controlled, though it has not beenpossible to sufficiently control the tilting thereof. This is because inaddition to the direction of the electrical field generated between thecomb-shaped third electrode 105 and the comb-shaped first electrode 103,an electrical field is generated between the second electrode 104 andthe comb-shaped first electrode 103. Thus, the tilting of the liquidcrystal material can be sufficiently controlled by providing pluralpairs of electrodes so as to generate plural directions of electricalfields therebetween.

Note that the substrate provided so as to face the insulating substrate100 may have a light-shielding layer which is overlapped with atransistor. The light-shielding layer is formed of, for example, aconductive material such as tungsten, chromium, or molybdenum; silicidesuch as tungsten silicide; or a resin material containing black pigmentor carbon black. In addition, a color filter is provided so as tooverlap with the comb-shaped first electrode 103 and the comb-shapedthird electrode 105. An alignment film is further provided over thecolor filter

The liquid crystal layer is provided between the insulating substrate100 and the counter substrate. A polarizing plate is provided over eachof the insulating substrate 100 and the counter substrate. Each of thepolarizing plates are provided over another side of the insulatingsubstrate 100 and the counter substrate which is different from the sidewhere the liquid crystal layer is provided.

Note that this embodiment mode shows an example where the descriptionsin Embodiment Modes 1 to 3 are realized together with a transistor.Therefore, the descriptions in Embodiment Modes 1 to 3 can be applied toor combined with this embodiment mode.

Embodiment Mode 5

In this embodiment mode, a structure of the liquid crystal displaydevice which is different from that described in the foregoingembodiment modes in that the common electrode is provided in the samelayer as the source and drain electrode in the thin film transistor isdescribed.

Note that a bottom gate transistor may be employed.

As shown in FIG. 2, a common electrode 122 is provided over theinsulating layer 106 to be in contact with a wire 121. The commonelectrode 122 can be formed similarly to the second electrode 104 in theforegoing Embodiment Mode 4.

As in FIG. 1, the comb-shaped third electrodes 105 and the comb-shapedfirst 103 are provided over the insulating layer 107 and the thirdelectrode 105 is connected to the common electrode 122 through anopening provided in the insulating layer 107.

The common electrode 122 is provided in contact with the wire 121 andthe third electrode 105 is electrically connected to the wire 121 aswell. Therefore, when the common electrode 122 and the third electrode105 are formed of a conductive material with high resistance compared toAl or the like, such as indium tin oxide (ITO), indium zinc oxide (IZO),indium tin oxide containing silicon oxide (ITSO), zinc oxide (ZnO), orsilicon (Si) containing phosphorus or boron, the wire 121 formed of Alor the like or a wire formed at the same time as the gate electrode 113can serve as an auxiliary wire of the common electrode 122 and the thirdelectrode 105. As a result, as described above, voltage drop caused bywire resistance of the common electrode 122 and the third electrode 105can be prevented.

At this time, it is desirable to use a conductive layer formed at thesame time as the gate electrode 113 as the auxiliary wire. In that case,the auxiliary wire is desirably placed so as to be approximatelyparallel to the gate wire, whereby an efficient layout can be achieved.

The description of other structures is omitted because it is similar tothat of FIG. 1.

When voltage is applied to such common electrode 122 and the comb-shapedfirst electrode 103, an electrical field is also generated therebetween.That is, electrical fields generate between the common electrode 122 andthe first electrode 103 and between the comb-shaped third electrode 105and the first electrode 103. Tilting of the liquid crystal material iscontrolled according to the electrical field between the two pair ofelectrodes, whereby the gray-scale display can be conducted. As aresult, in a part of the liquid crystal material, whose tilting has notbeen sufficiently controlled by an electrical field generated by onepair of electrodes of the comb-shaped third electrode 105 and thecomb-shaped first electrode 103, tilting of the liquid crystal materialcan be sufficiently controlled by electrical fields generated by twopairs of electrodes. Specifically, by providing the common electrode122, the tilting of the liquid crystal material right above thecomb-shaped third electrode 105 or comb-shaped first electrode 103 canbe sufficiently controlled, though it has not been possible tosufficiently control the tilting thereof.

Thus, the tilting of the liquid crystal material can be sufficientlycontrolled by providing plural pairs of electrodes so as to generateplural directions of electrical fields therebetween. In addition, inthis embodiment mode, since the common electrode 122 is formed over theinsulating layer 106, the distance between the common electrode 122 andthe first electrode 103 becomes shorter, whereby voltage to be appliedcan be reduced.

Note that this embodiment mode shows an example where the descriptionsin Embodiment Modes 1 to 3 are realized together with a transistor andwhich is a modification of that in Embodiment Mode 4. Therefore, thedescriptions in Embodiment Modes 1 to 4 can be applied to or combinedwith this embodiment mode.

Embodiment Mode 6

In this embodiment mode, a structure of the liquid crystal displaydevice which is different from that described the foregoing embodimentmode in that the common electrode is provided over the base layer 101 isdescribed.

As shown in FIG. 3, the base layer 101 is provided over the insulatingsubstrate 100 and a common electrode 132 is formed thereover. The commonelectrode 132 can be formed similarly to the second electrode 104 in theforegoing Embodiment Mode. The insulating layer 106 is provided over thecommon electrode 132 and the common electrode 132 is connected to thethird electrode 105 through an opening provided in the insulating layer106. Therefore, when the common electrode 132 and the third electrode105 are formed of a conductive material with high resistance compared toAl or the like, such as indium tin oxide (ITO), indium zinc oxide (IZO),indium tin oxide containing silicon oxide (ITSO), zinc oxide (ZnO), orsilicon (Si) containing phosphorus or boron, a wire 131 formed of Al orthe like can serve as an auxiliary wire or wire. As a result, asdescribed above, voltage drop caused by wire resistance of the commonelectrode 132 and the third electrode 105 can be prevented. The wire 131can be formed by the same conductive layer as the gate electrode 113. Inthat case, the auxiliary wire is desirably placed so as to beapproximately parallel to the gate wire, whereby an efficient layout canbe achieved.

Note that a bottom gate transistor may be employed in this embodimentmode.

The description of other structures is omitted because it is similar tothat of FIG. 1.

When voltage is applied to such common electrode 132 and the comb-shapedfirst electrode 103, an electrical field is also generated therebetween.That is, electrical fields generate between the common electrode 132 andthe first electrode 103 and between the comb-shaped third electrode 105and the first electrode 103. Tilting of the liquid crystal material iscontrolled according to the electrical field between the two pair ofelectrodes, whereby the gray-scale display can be conducted. As aresult, in a part of the liquid crystal material, whose tilting has notbeen sufficiently controlled by an electrical field generated by onepair of electrodes of the comb-shaped third electrode 105 and thecomb-shaped first electrode 103, tilting of the liquid crystal materialcan be sufficiently controlled by electrical fields generated by twopairs of electrodes. Specifically, by providing the common electrode132, the tilting of the liquid crystal material right above thecomb-shaped third electrode 105 or comb-shaped first electrode 103 canbe sufficiently controlled, though it has not been possible tosufficiently control the tilting thereof.

Thus, the tilting of the liquid crystal material can be sufficientlycontrolled by providing plural pairs of electrodes so as to generateplural directions of electrical fields therebetween. In addition, inthis embodiment mode, since the common electrode 122 is formed over thebase layer 101, the insulating layer 106 can serve as a single-layerstructure as it is. As a result, the distance between the commonelectrode 132 and the first electrode 103 becomes shorter, wherebyvoltage to be applied can be reduced.

Note that this embodiment mode shows an example where the descriptionsin Embodiment Modes 1 to 3 are realized together with a transistor andwhich is a modification of that in Embodiment Mode 4 or 5. Therefore,the descriptions in Embodiment Modes 1 to 5 can be applied to orcombined with this embodiment mode.

Embodiment Mode 7

In this embodiment mode, a structure of the liquid crystal displaydevice which is different from that described in the foregoingembodiment mode in that an amorphous semiconductor layer is used as thesemiconductor layer in the thin film transistor is described.

As shown in FIG. 4, a thin film transistor 160 including an amorphoussemiconductor layer is formed over the base layer 101. The thin filmtransistor 160 is a so-called bottom gate type in which a semiconductorlayer is provided below a gate electrode.

The gate electrode 113 is formed over the base layer 101 and the gateinsulating layer 112 is formed so as to cover the gate electrode 113. Anamorphous semiconductor layer 411 is formed over the gate electrode withthe gate insulating layer 112 therebetween. The amorphous semiconductorlayer 411 can be formed of a material containing silicon.

The source and drain electrodes 116 are formed to cover both edges ofthe amorphous semiconductor layer 411. In order to reduce wireresistance, an N-type impurity region is preferably formed in a regionin the amorphous semiconductor layer, which is in contact with thesource and drain electrodes. The N-type impurity region can be formed byadding an impurity to the surface of the amorphous semiconductor layer411.

After that, the amorphous semiconductor layer 411 is processed into apredetermined shape using the source and drain electrodes. At this time,a portion over a channel forming region in the semiconductor layer inthe thin film transistor 160 is removed by etching. A thin filmtransistor with such a structure is called a channel etched thin filmtransistor.

The insulating layer 106 is formed to cover the thin film transistor 160formed in this manner. The use of an organic material for the insulatinglayer 106 can improve flatness of the surface thereof. Needles to say,an inorganic material can be used for the insulating layer 106 or astacked-layer structure including an inorganic material and an organicmaterial can be used. An opening is formed in the insulating layer 106to expose the source and drain electrodes 116, whereby the firstelectrode 103 formed over the insulating layer 106 and the source anddrain electrodes 116 are electrically connected. The first electrode 103is formed to be comb-shaped over the insulating layer 106 as in theforegoing embodiment mode.

Then, description is made of a structure of a common electrode 401. Thecommon electrode 401 is formed over the base layer 101. The commonelectrode 401 can be formed like the second electrode 104 shown in theforegoing embodiment mode. The common electrode 401 has its shapeprocessed so as to be formed over the pixel region. A conductive layer402 is formed in a part of the processed common electrode 401. Theconductive layer 402 can be obtained by processing the same conductivelayer as the gate electrode 113 in the thin film transistor 160. Thecommon electrode 401 and the conductive layer 402 are covered with thegate insulating layer 112.

An opening is provided in the insulating layer 106 and the gateinsulating layer 112 to expose the conductive layer 402. Then, thecomb-shaped third electrode 105 formed over the insulating layer 106 andthe conductive layer 402 are electrically connected. As a result, thethird electrode 105 and the common electrode 401 are connected. Here,the conductive layer 402 is connected to the common electrode 401 andthe third electrode 105; therefore, the conductive layer 402 can serveas the auxiliary wire. Then, as described above, voltage drop caused bywire resistance of the common electrode 401 and the third electrode 105can be prevented.

In this embodiment mode, since a bottom gate thin film transistor usingan amorphous semiconductor layer is used, the whole thickness can bereduced compared to a top gate thin film transistor in the foregoingembodiment mode. In particular, compared with a structure including thestacked insulating layers 106 and 107, the whole thickness of thestructure in this embodiment mode is thin since only the insulatinglayer 106 is employed. As a result, the liquid crystal display devicecan be thin and light weight.

Although the channel etched type is employed in this embodiment mode, achannel protective type may be employed. In the channel protective type,a protective layer is provided over the semiconductor layer and thesource and drain electrodes are provided on both sides of the protectivelayer, in which the surface of the semiconductor layer is not removedwhen processing the semiconductor layer.

Note that a top gate transistor may be employed in this embodiment mode.

Note that this embodiment mode shows an example where the descriptionsin Embodiment Modes 1 to 3 are realized together with a transistor andwhich is a modification of those in Embodiment Mode 4 to 6. Therefore,the descriptions in Embodiment Modes 1 to 6 can be applied to orcombined with this embodiment mode.

Embodiment Mode 8

In this embodiment mode, a structure of the liquid crystal displaydevice which is different from that described in the foregoingembodiment mode in that the conductive layer serving as the auxiliarywire is provided below the common electrode is described.

As shown in FIG. 5, a conductive layer 502 is formed over the base layer101 in advance. After that, a common electrode 501 is formed to be incontact with the conductive layer 502. The common electrode 501 can beformed similarly to the second electrode 104 in the foregoing embodimentmode. The conductive layer 502 can be obtained by processing the sameconductive layer as the gate electrode 113 in the thin film transistor160 or the same conductive layer as the source and drain electrodes 116.The conductive layer 502 and the common electrode 501 are covered withthe insulating layer 106.

An opening is provided in the insulating layer 106 and the gateinsulating layer 112 to expose the common electrode 501. Then, thecomb-shaped third electrode 105 formed over the insulating layer 106 andthe common electrode 501 are electrically connected. Here, theconductive layer 502 is connected to the common electrode 401 and thethird electrode 105; therefore, the conductive layer 502 can serve asthe auxiliary wire. Then, as described above, voltage drop caused bywire resistance of the common electrode 501 and the third electrode 105can be prevented.

Description of other structures is omitted because it is similar to thatof FIG. 4.

In this embodiment mode, a structure in which only the insulating layer106 is employed, therefore, the whole thickness of the structure is thincompared to a structure including the stacked insulating layers 106 and107. As a result, the liquid crystal display device can be thin andlight weight.

Although the channel etched type thin film transistor is employed inthis embodiment mode, a channel protective type thin film transistor maybe employed as described in the foregoing embodiment mode.

Note that this embodiment mode shows an example where the descriptionsin Embodiment Modes 1 to 3 are realized together with a transistor andwhich is a modification of those in Embodiment Modes 4 to 7. Therefore,the descriptions in Embodiment Modes 1 to 7 can be applied to orcombined with this embodiment mode.

Embodiment Mode 9

In this embodiment mode, a structure of the liquid crystal displaydevice which is different from that in foregoing Embodiment Mode 1 inthat a color filter and a black matrix are provided is described.

As shown in FIG. 6A, in the structure of the liquid crystal displaydevice shown in Embodiment Mode 1 (FIG. 1), a color filter 150 and ablack matrix 151 are provided instead of the insulating layer 107. Thecolor filter 150 and the black matrix 151 are provided so as to bepartially overlapped with each other.

The color filter 150 is formed of a material with which predeterminedcolors can be exhibited. Red, green, and blue are generally used as thepredetermined colors. Combination of these colors realizes full colordisplay. On the other hand when conducting single color display, thecolor filter can be formed of a material with which one color of red,green, or blue, alternatively, orange or yellow can be exhibited. Singlecolor display is suitable for displaying simple letters and figure andmay be used for a display screen of a car audio or portable audiodevice.

The black matrix 151 is provided to prevent the thin film transistor 102from being irradiated with light, suppress reflection of an electrodeincluded in the thin film transistor 102, prevent light from leaking ina portion where the liquid crystal molecule is not controlled by animage signal, and divide one pixel. The black matrix 151 is acceptableas long as it exhibits black and may be formed using a conductive layercontaining chromium or an organic material containing pigment or blackcarbon. In addition, the black matrix 151 can be formed of a dyedorganic material such as acrylic or polyimide can be used.

Note that the black matrix 151 is desirably formed of a nonconductivematerial so as not to affect application of an electrical field.

When providing the color filter 150 and the black matrix 151, it isdesirable that the insulating layer 106 have a stacked-layer structureand an insulating layer be formed of an inorganic material and anorganic material formed as an upper layer thereof. The color filter 150and the black matrix black matrix 151 are often formed of an organicmaterial and these materials contain impurity elements which is notfavorable to electric characteristics of the thin film transistor. It isdesirable to form the insulating layer to prevent entry of the impurityelements to the semiconductor layer 111 in the thin film transistor.

Therefore, silicon nitride is preferable as an inorganic material forforming the insulating layer. Such an insulating layer is also called apassivation layer. The passivation layer is not limited to be providedover the insulating layer 106 having a stacked-layer structure. It isacceptable as long as the passivation layer is provided between thesemiconductor layer 111, and the color filter 150 and the black matrix151. For example, the passivation layer may be provided as a lower layerof the insulating layer 106 having a stacked-layer structure.

Note that an inorganic material such as silicon nitride may be depositedbefore forming the color filter 150 and the black matrix 151.

After that, an insulating layer 152 is formed to cover the color filter150 and the black matrix 151. The insulating layer 152 flattens thesurface. In particular, in a region where the color filter 150 and theblack matrix 151 are overlapped with each other, a step formed becauseof the thickness of the black matrix 151 can be flattened by theinsulating layer 152.

Description of other structures is omitted because it is similar to thatof FIG. 1.

A structure shown in FIG. 6B is different from that shown in FIG. 6A inthat the color filter 150 and the black matrix 151 are provided so asnot to overlap with each other. The color filter 150 is providedproactively in a region where light is transmitted and the black matrix151 is proactively provided in a region including the thin filmtransistor 102. As a result, with a boundary of a boundary region of thethin film transistor 102 and the second electrode 104, the color filter150 is formed in a region in which the second electrode 104 is formedand the black matrix 151 is formed in a region in which the thin filmtransistor 102 is formed. Then, the insulating layer 152 is formed tocover the color filter 150 and the black matrix 151.

It is preferable to provide the color filter 150 and the black matrix151 without them overlapping with each other since the whole thicknessis increased in the region where they are overlapped.

Description of other structures is omitted because it is similar to thatof FIG. 6A.

A structure shown in FIG. 6C is different from those in FIGS. 6A and 6Bin that the black matrix 151 is provided on the counter substrate 155. Aregion where the black matrix 151 is provided is not limited as long asit is over the thin film transistor 102.

In this case, color filters of different colors in neighboring pixelsmay be arranged to overlap with each other. In a region where the colorfilters are stacked can serve as the black matrix since itstransmittance is reduced.

When the black matrix 151 is provided to the counter substrate 155, thecolor filter 150 can be formed over the thin film transistor 102 and thesecond electrode 104. As described above, the color filter 150 is formedusing an organic material; therefore, the color filter 150 also servesas a flattening film. That is, the color filter 150 can be providedinstead of an insulating layer 107, and the surface of the color filter150 can be flattened.

Note that the black matrix 151 may be provided on a rear surface side ofthe insulating substrate 100.

Note that the black matrix may be provided on the insulating substrate100 side and the color filter is formed on the counter substrate side.By providing the black matrix on the insulating substrate 100 side,margin of arrangement in substrates can be improved.

Description of other structures is omitted because it is similar to thatof FIG. 6A.

In this embodiment mode, as in Embodiment Mode 1, when voltage isapplied to the second electrode 104 and the comb-shaped first electrode103, an electrical field is generated therebetween. Therefore, tiltingof the liquid crystal material can be controlled, whereby gray-scaledisplay can be conducted. As a result, in a part of the liquid crystalmaterial, whose tilting has not been sufficiently controlled by anelectrical field generated by one pair of electrodes of the comb-shapedthird electrode 105 and the comb-shaped first electrode 103, tilting ofthe liquid crystal material can be sufficiently controlled by electricalfields generated by two pairs of electrodes.

Note that this embodiment mode shows an example where the descriptionsin Embodiment Modes 1 to 3 are realized together with a transistor andwhich is a modification of those in Embodiment Modes 4 to 8. Therefore,the descriptions in Embodiment Modes 1 to 8 can be applied to orcombined with this embodiment mode.

Embodiment Mode 10

In this embodiment mode, a structure of the liquid crystal displaydevice which is different from that in foregoing Embodiment Mode 1 inthat the color filter 150 and the black matrix 151 are provided insteadof the insulating layer 106 is described.

As shown in FIG. 7A, in the structure of the liquid crystal displaydevice shown in Embodiment Mode 1 (FIG. 1), the color filter 150 and theblack matrix 151 are provided instead of the insulating layer 106. Thecolor filter 150 and the black matrix 151 are provided so as to bepartially overlapped with each other. The color filter 150 and the blackmatrix 151 can be formed similarly to those in the foregoing embodimentmode. The insulating layer 152 is formed to cover the color filter 150and the black matrix 151. The surface can be flattened by the insulatinglayer 152.

In the case of providing the color filter 150 and the black matrix 151,a passivation layer is desirably provided between the color filter 150and the black matrix 151, and the semiconductor layer 111 in the thinfilm transistor 102. In this embodiment mode, a passivation layer 154 isformed to cover the gate electrode 113 and the second electrode 104.

In such a structure where the color filter 150 and the black matrix 151are provided instead of the insulating layer 106, the black matrix 151is formed in a vicinity of the thin film transistor 102. Therefore, thestructure is preferable since light emitted to the thin film transistor102 is shielded effectively.

Description of other structures is omitted because it is similar to thatof FIG. 6A.

A structure shown in FIG. 7B is different from that in FIG. 7A in thatthe color filter 150 and the black matrix 151 are provided so as not tooverlap with each other.

Description of other structures is omitted because it is similar to thatof FIG. 6B.

A structure shown in FIG. 7C is different from those in FIGS. 7A and 7Bin that the black matrix 151 is provided on the counter substrate 155side.

Description of other structures is omitted because it is similar to thatof FIG. 7B.

In this embodiment mode, as in Embodiment Mode 1, when voltage isapplied to the second electrode 104 and the comb-shaped first electrode103, an electrical field is generated therebetween. Therefore, tiltingof the liquid crystal material can be controlled, whereby gray-scaledisplay can be conducted. As a result, in a part of the liquid crystalmaterial, whose tilting has not been sufficiently controlled by anelectrical field generated by one pair of electrodes of the comb-shapedthird electrode 105 and the comb-shaped first electrode 103, tilting ofthe liquid crystal material can be sufficiently controlled by electricalfields generated by two pairs of electrodes.

Note that this embodiment mode shows an example where the descriptionsin Embodiment Modes 1 to 3 are realized together with a transistor andwhich is a modification of those in Embodiment Modes 4 to 9. Therefore,the descriptions in Embodiment Modes 1 to 9 can be applied to orcombined with this embodiment mode.

Embodiment Mode 11

In this embodiment mode, a structure of the liquid crystal displaydevice which is different from that in foregoing Embodiment Mode 2 inthat the color filter and the black matrix are provided is described.

As shown in FIG. 8A, in the structure of the liquid crystal displaydevice shown in Embodiment Mode 2 (FIG. 2), the color filter 150 and theblack matrix 151 are provided instead of the insulating layer 107. Thecolor filter 150 and the black matrix 151 are provided so as to bepartially overlapped with each other. The color filter 150 and the blackmatrix 151 can be formed similarly to those in the foregoing embodimentmode. The insulating layer 152 is formed to cover the color filter 150and the black matrix 151. The surface can be flattened by the insulatinglayer 152.

In the case of providing the color filter 150 and the black matrix 151,a passivation layer is desirably provided between the color filter 150and the black matrix 151, and the semiconductor layer 111 in the thinfilm transistor 102. In this embodiment mode, the insulating layer 106has a stacked-layer structure and an upper layer thereof is apassivation layer 153 formed of an inorganic material. The passivationlayer is not limited to be provided as the upper layer of the insulatinglayer 106 having a stacked-layer structure. It is acceptable as long asthe passivation layer is provided between the semiconductor layer 111,and the color filter 150 and the black matrix 151. For example, thepassivation layer may be provided as a lower layer of the insulatinglayer 106 having a stacked-layer structure.

Those structures of the color filter 150, the black matrix 151, theinsulating layer 152, and the passivation layer 153 are similar to thoseshown in FIG. 6A. Description of other structures is omitted because itis similar to that of FIG. 2.

A structure shown in FIG. 8B is different from that in FIG. 8A in thatthe color filter 150 and the black matrix 151 are provided so as not tooverlap with each other. Structures of the color filter 150 and theblack matrix 151 which are not overlapped with each other is similar tothose shown in FIG. 6B.

Description of other structures is omitted because it is similar to thatof FIG. 8A.

A structure shown in FIG. 8C is different from those shown in FIGS. 8Aand 8B in that the black matrix 151 is provided on the counter substrate155 side. A region where the black matrix 151 is provided is not limitedas long as is over the thin film transistor 102.

When the black matrix 151 is provided to the counter substrate 155, thecolor filter 150 can be formed over the thin film transistor 102 and thesecond electrode 104. As described above, the color filter 150 is formedusing an organic material; therefore, the color filter 150 also servesas a flattening film. That is, the color filter 150 can be providedinstead of the insulating layer 107, and the surface of the color filter150 can be flattened. Such a structure in which the black matrix 151 isprovided on the counter substrate 155 side is similar to that shown inFIG. 6C.

Note that the black matrix 151 may be provided on the rear surface sideof the insulating substrate 100.

Description of other structures is omitted because it is similar to thatof FIG. 8A.

In this embodiment mode, as in Embodiment Mode 2, when voltage isapplied to the common electrode 122 and the comb-shaped first electrode103, an electrical field is generated therebetween. Therefore, tiltingof the liquid crystal material can be controlled, whereby gray-scaledisplay can be conducted. As a result, in a part of the liquid crystalmaterial, whose tilting has not been sufficiently controlled by anelectrical field generated by one pair of electrodes of the comb-shapedthird electrode 105 and the comb-shaped first electrode 103, tilting ofthe liquid crystal material can be sufficiently controlled by electricalfields generated by two pairs of electrodes.

Note that this embodiment mode shows an example where the descriptionsin Embodiment Modes 1 to 3 are realized together with a transistor andwhich is a modification of those in Embodiment Modes 4 to 10. Therefore,the descriptions in Embodiment Modes 1 to 10 can be applied to orcombined with this embodiment mode.

Embodiment Mode 12

In this embodiment mode, a structure of the liquid crystal displaydevice which is different from that in foregoing Embodiment Mode 2 inthat the color filter and the black matrix are provided instead of theinsulating layer 106 is described.

As shown in FIG. 9A, in the structure of the liquid crystal displaydevice shown in Embodiment Mode 2 (FIG. 2), the color filter 150 and theblack matrix 151 are provided instead of the insulating layer 106. Thecolor filter 150 and the black matrix 151 are provided so as to bepartially overlapped with each other. The color filter 150 and the blackmatrix 151 can be formed similarly to those in the foregoing embodimentmode. The insulating layer 152 is formed to cover the color filter 150and the black matrix 151. The surface can be flattened by the insulatinglayer 152.

In the case of providing the color filter 150 and the black matrix 151,a passivation layer is desirably provided between the color filter 150and the black matrix 151, and the semiconductor layer 111 in the thinfilm transistor 102. In this embodiment mode, the passivation layer 154is formed to cover the gate electrode 113 and the second electrode 104.

Such a structure of providing the color filter 150 and the black matrix151 is similar to that shown in FIG. 7A. Description of other structuresis omitted because it is similar to that of FIG. 2.

A structure shown in FIG. 9B is different from that in FIG. 9A in thatthe color filter 150 and the black matrix 151 are provided so as not tooverlap with each other. Structures of the color filter 150 and theblack matrix 151 which are not overlapped with each other is similar tothose shown in FIG. 7B.

Description of other structures is omitted because it is similar to thatof FIG. 9A.

A structure shown in FIG. 9C is different from those in FIGS. 9A and 9Bin that the black matrix 151 is provided on the counter substrate 155side. A region where the black matrix 151 is provided is not limited aslong as it is over the thin film transistor 102.

When the black matrix 151 is provided to the counter substrate 155, thecolor filter 150 can be formed over the thin film transistor 102 and thesecond electrode 104. As described above, the color filter 150 is formedusing an organic material; therefore, the color filter 150 also servesas a flattening film. That is, the color filter 150 can be providedinstead of the insulating layer 107, and the surface of the color filter150 can be flattened. Such a structure in which the black matrix 151 isprovided on the counter substrate 155 side is similar to that shown inFIG. 7C.

Note that the black matrix 151 may be provided on the rear surface sideof the insulating substrate 100.

Description of other structures is omitted because it is similar to thatof FIG. 9A.

In this embodiment mode, as in Embodiment Mode 2, when voltage isapplied to the common electrode 122 and the comb-shaped first electrode103, an electrical field is generated therebetween. Therefore, tiltingof the liquid crystal material can be controlled so as to conductgray-scale display. As a result, in a part of the liquid crystalmaterial, whose tilting has not been sufficiently controlled by anelectrical field generated by one pair of electrodes of the comb-shapedthird electrode 105 and the comb-shaped first electrode 103, tilting ofthe liquid crystal material can be sufficiently controlled by electricalfields generated by two pairs of electrodes.

Note that this embodiment mode shows an example where the descriptionsin Embodiment Modes 1 to 3 are realized together with a transistor andwhich is a modification of those in Embodiment Modes 4 to 11. Therefore,the descriptions in Embodiment Modes 1 to 11 can be applied to orcombined with this embodiment mode.

Embodiment Mode 13

In this embodiment mode, a structure of the liquid crystal displaydevice which is different from that in foregoing Embodiment Mode 3 inthat the color filter and the black matrix are provided instead of theinsulating layer 106 is described.

As shown in FIG. 10A, in the structure of the liquid crystal displaydevice shown in Embodiment Mode 3 (FIG. 3), the color filter 150 and theblack matrix 151 are provided instead of the insulating layer 106. Thecolor filter 150 and the black matrix 151 are provided so as to bepartially overlapped with each other. The color filter 150 and the blackmatrix 151 can be formed similarly to those in the foregoing embodimentmode. The insulating layer 152 is formed to cover the color filter 150and the black matrix 151. The surface can be flattened by the insulatinglayer 152.

In the case of providing the color filter 150 and the black matrix 151,a passivation layer is desirably provided between the color filter 150and the black matrix 151, and the semiconductor layer 111 in the thinfilm transistor 102. In this embodiment mode, the passivation layer 154is formed to cover the gate electrode 113 and the second electrode 104.

Such a structure of providing the color filter 150 and the black matrix151 is similar to that shown in FIG. 7A. Description of other structuresis omitted because it is similar to that of FIG. 3.

A structure shown in FIG. 10B is different from that in FIG. 10A in thatthe color filter 150 and the black matrix 151 are provided so as not tooverlap with each other. Structures of the color filter 150 and theblack matrix 151 which are not overlapped with each other is similar tothose shown in FIG. 7B.

Description of other structures is omitted because it is similar to thatof FIG. 10A.

A structure shown in FIG. 10C is different from those in FIGS. 10A and10B in that the black matrix 151 is provided on the counter substrate155 side. A region where the black matrix 151 is provided is not limitedas long as it is over the thin film transistor 102.

When the black matrix 151 is provided to the counter substrate 155, thecolor filter 150 can be formed over the thin film transistor 102 and thesecond electrode 104. As described above, the color filter 150 is formedusing an organic material; therefore, the color filter 150 also servesas a flattening film. That is, the color filter 150 can be providedinstead of the insulating layer 107, and the surface of the color filter150 can be flattened. Such a structure in which the black matrix 151 isprovided on the counter substrate 155 side is similar to that shown inFIG. 7C.

Note that the black matrix 151 may be provided on the rear surface sideof the insulating substrate 100.

The description of other structures is omitted because it is similar tothat of FIG. 10A.

In this embodiment mode, as in Embodiment Mode 3, when voltage isapplied to the common electrode 122 and the comb-shaped first electrode103, an electrical field is generated therebetween. Therefore, tiltingof the liquid crystal material can be controlled so as to conductgray-scale display. As a result, in a part of the liquid crystalmaterial, whose tilting has not been sufficiently controlled by anelectrical field generated by one pair of electrodes of the comb-shapedthird electrode 105 and the comb-shaped first electrode 103, tilting ofthe liquid crystal material can be sufficiently controlled by electricalfields generated by two pairs of electrodes.

Note that this embodiment mode shows an example where the descriptionsin Embodiment Modes 1 to 3 are realized together with a transistor andwhich is a modification of those in Embodiment Modes 4 to 12. Therefore,the descriptions in Embodiment Modes 1 to 12 can be applied to orcombined with this embodiment mode.

Embodiment Mode 14

In this embodiment mode, a structure of the liquid crystal displaydevice which is different from that in foregoing Embodiment Mode 4 inthat the color filter and the black matrix are provided instead of theinsulating layer 106 is described.

As shown in FIG. 11A, in the structure of the liquid crystal displaydevice shown in Embodiment Mode 4 (FIG. 4), the color filter 150 and theblack matrix 151 are provided instead of the insulating layer 106. Thecolor filter 150 and the black matrix 151 are provided so as to bepartially overlapped with each other. The color filter 150 and the blackmatrix 151 can be formed similarly to those in the foregoing embodimentmode. The insulating layer 152 is formed to cover the color filter 150and the black matrix 151. The surface can be flattened by the insulatinglayer 152.

In this embodiment mode, the thin film transistor 160 is preferably achannel protective type in which an insulating layer 403 is providedover the amorphous semiconductor layer 411. The source and drainelectrodes 116 are provided so as to cover both edges of the insulatinglayer 403 for protecting a channel. The insulating layer 403 preventsthe amorphous semiconductor layer 411 from being exposed. Accordingly,when the black matrix 151 is provided to cover the thin film transistor160, entry of impurity elements from the black matrix to the amorphoussemiconductor layer 411 can be prevented. Needles to say, the thin filmtransistor 160 may be a channel etched type as shown in Embodiment Mode4; in that case, the insulating layer 403 is desirably provided so thatthe amorphous semiconductor layer 411 and the black matrix 151 are notin contact with each other.

In the case of providing the color filter 150 and the black matrix 151,a passivation layer is desirably provided between the color filter 150and the black matrix 151, and the amorphous semiconductor layer 411 inthe thin film transistor 160. In this embodiment mode, the passivationlayer 154 is formed to cover the gate electrode 113, the commonelectrode 401, and the conductive layer 402.

Such a structure of providing the color filter 150 and the black matrix151 is similar to that shown in FIG. 7A. Description of other structuresis omitted because it is similar to that of FIG. 4.

A structure shown in FIG. 11B is different from that in FIG. 11A in thatthe color filter 150 and the black matrix 151 are provided so as not tooverlap with each other. Structures of the color filter 150 and theblack matrix 151 which are not overlapped with each other is similar tothose shown in FIG. 7B.

Description of other structures is omitted because it is similar to thatof FIG. 11A.

A structure shown in FIG. 11C is different from those in FIGS. 11A and11B in that the black matrix 151 is provided on the counter substrate155 side. A region where the black matrix 151 is provided is not limitedas long as it is over the thin film transistor 160.

When the black matrix 151 is provided to the counter substrate 155, thecolor filter 150 can be formed over the thin film transistor 160, thecommon electrode 401, and the conductive layer 402.

In this embodiment mode, the thin film transistor 160 is preferably achannel protective type in which the insulating layer 403 is providedover the amorphous semiconductor layer 411. The source and drainelectrodes 116 are provided so as to cover both edges of the insulatinglayer 403 for protecting a channel. The insulating layer 403 preventsthe amorphous semiconductor layer 411 from being exposed. Accordingly,when the color filter 150 is provided to cover the thin film transistor160, entry of impurity elements from the color filter to the amorphoussemiconductor layer 411 can be prevented. Needles to say, the thin filmtransistor 160 may be a channel etched type as shown in Embodiment Mode4; in that case, the insulating layer 403 is desirably provided so thatthe amorphous semiconductor layer 411 and the color filter 150 are notin contact with each other.

As described above, the color filter 150 is formed of an organicmaterial; therefore, the color filter 150 also serves as a flatteningfilm. That is, the color filter 150 can be provided instead of theinsulating layer 106, and the surface of the color filter 150 can beflattened. The structure of providing the black matrix 151 on thecounter substrate 155 side is similar to that shown in FIG. 7C.

Note that the black matrix 151 may be provided on the rear surface sideof the insulating substrate 100.

Description of other structures is omitted because it is similar to thatof FIG. 11A.

In this embodiment mode, as in Embodiment Mode 3, when voltage isapplied to the common electrode 401 and the comb-shaped first electrode103, an electrical field is generated therebetween. Therefore, tiltingof the liquid crystal material can be controlled so as to conductgray-scale display. As a result, in a part of the liquid crystalmaterial, whose tilting has not been sufficiently controlled by anelectrical field generated by one pair of electrodes of the comb-shapedthird electrode 105 and the comb-shaped first electrode 103, tilting ofthe liquid crystal material can be sufficiently controlled by electricalfields generated by two pairs of electrodes.

Note that this embodiment mode shows an example where the descriptionsin Embodiment Modes 1 to 3 are realized together with a transistor andwhich is a modification of those in Embodiment Modes 4 to 13. Therefore,the descriptions in Embodiment Modes 1 to 13 can be applied to orcombined with this embodiment mode.

Embodiment Mode 15

In this embodiment mode, a structure of the liquid crystal displaydevice which is different from that in foregoing Embodiment Mode 5 inthat the color filter and the black matrix are provided instead of theinsulating layer 106 is described.

As shown in FIG. 12A, in the structure of the liquid crystal displaydevice shown in Embodiment Mode 5 (FIG. 5), the color filter 150 and theblack matrix 151 are provided instead of the insulating layer 106. Thecolor filter 150 and the black matrix 151 are provided so as to bepartially overlapped with each other. The color filter 150 and the blackmatrix 151 can be formed similarly to those in the foregoing embodimentmode. The insulating layer 152 is formed to cover the color filter 150and the black matrix 151. The surface can be flattened by the insulatinglayer 152.

In this embodiment mode, the thin film transistor 160 is preferably achannel protective type in which the insulating layer 403 is providedover the amorphous semiconductor layer 411. The source and drainelectrodes 116 are provided so as to cover both edges of the insulatinglayer 403 for protecting a channel. The insulating layer 403 preventsthe amorphous semiconductor layer 411 from being exposed. Accordingly,when the black matrix 151 is provided to cover the thin film transistor160, entry of impurity elements from the black matrix to the amorphoussemiconductor layer 411 can be prevented. Needles to say, the thin filmtransistor 160 may be a channel etched type as shown in Embodiment Mode4; in that case, the insulating layer 403 is desirably provided so thatthe amorphous semiconductor layer 411 and the black matrix 151 are notin contact with each other.

In the case of providing the color filter 150 and the black matrix 151,a passivation layer is desirably provided between the color filter 150and the black matrix 151, and the amorphous semiconductor layer 411 inthe thin film transistor 160. In this embodiment mode, the passivationlayer 154 is formed to cover the gate electrode 113, the commonelectrode 401, and the conductive layer 402.

Such a structure of providing the color filter 150 and the black matrix151 is similar to that shown in FIG. 7A. The description of otherstructures is omitted because it is similar to that of FIG. 5

A structure shown in FIG. 12B is different from that in FIG. 12A in thatthe color filter 150 and the black matrix 151 are provided so as not tooverlap with each other. Structures of the color filter 150 and theblack matrix 151 which are not overlapped with each other is similar tothose shown in FIG. 7B.

The description of other structures is omitted because it is similar tothat of FIG. 12A.

A structure shown in FIG. 12C is different from those in FIGS. 12A and12B in that the black matrix 151 is provided on the counter substrate155 side. A region where the black matrix 151 is provided is not limitedas long as it is over the thin film transistor 160.

When the black matrix 151 is provided to the counter substrate 155, thecolor filter 150 can be formed over the thin film transistor 160, thecommon electrode 401, and the conductive layer 402.

In this embodiment mode, the thin film transistor 160 is preferably achannel protective type in which the insulating layer 403 is providedover the amorphous semiconductor layer 411. The source and drainelectrodes 116 are provided so as to cover both edges of the insulatinglayer 403 for protecting a channel. The insulating layer 403 preventsthe amorphous semiconductor layer 411 from being exposed. Accordingly,when the color filter 150 is provided to cover the thin film transistor160, entry of impurity elements from the color filter to the amorphoussemiconductor layer 411 can be prevented. Needles to say, the thin filmtransistor 160 may be a channel etched type as shown in Embodiment Mode4; in that case, the insulating layer 403 is desirably provided so thatthe amorphous semiconductor layer 411 and the color filter 150 are notin contact with each other.

As described above, the color filter 150 is formed of an organicmaterial; therefore, the color filter 150 also serves as a flatteningfilm. That is, the color filter 150 can be provided instead of theinsulating layer 106, and the surface of the color filter 150 can beflattened. The structure of providing the black matrix 151 on thecounter substrate 155 side is similar to that shown in FIG. 7C.

Note that the black matrix 151 may be provided on the rear surface sideof the insulating substrate 100.

The description of other structures is omitted because it is similar tothat of FIG. 12A.

In this embodiment mode, as in Embodiment Mode 3, when voltage isapplied to the common electrode 401 and the comb-shaped first electrode103, an electrical field is generated therebetween. Therefore, tiltingof the liquid crystal material can be controlled so as to conductgray-scale display. As a result, in a part of the liquid crystalmaterial, whose tilting has not been sufficiently controlled by anelectrical field generated by one pair of electrodes of the comb-shapedthird electrode 105 and the comb-shaped first electrode 103, tilting ofthe liquid crystal material can be sufficiently controlled by electricalfields generated by two pairs of electrodes.

Note that this embodiment mode shows an example where the descriptionsin Embodiment Modes 1 to 3 are realized together with a transistor andwhich is a modification of those in Embodiment Modes 4 to 14. Therefore,the descriptions in Embodiment Modes 1 to 14 can be applied to orcombined with this embodiment mode.

Embodiment Mode 16

In this embodiment mode, a top view of a pixel portion in a liquidcrystal display device is described.

FIG. 13 shows a top view corresponding to the cross-sectional structureshown in Embodiment Mode 4 (FIG. 4). The thin film transistor (alsoreferred to as TFT) 160 includes the amorphous semiconductor layer 411and has a bottom gate structure in which the gate electrode 113 isprovided below. A scan line 413 can be formed in the same layer as thegate electrode 113.

The amorphous semiconductor layer 411 is formed to cover the gateelectrode 113. The common electrode 401 can be formed using theamorphous semiconductor layer 411. Note that since the common electrode401 is desirably formed of a material with high conductivity, animpurity element is preferably added to the semiconductor layer. Thecommon electrode 401 may be formed of a conductive material withoutusing the amorphous semiconductor layer 411.

The source and drain electrodes 116 are formed so as to cover both edgesof the amorphous semiconductor layer 411. A signal line 416 can beformed in the same layer as the source and drain electrodes 116.

The first electrode 103 and the third electrode 105 are formed in thesame layer. The first electrode 103 and the third electrode 105 areprocessed into comb-shapes and are arranged alternately. The firstelectrode 103 is connected to either the source and drain electrodes 116through an opening. The third electrode 105 is connected to the commonelectrode 401 through an opening.

In the same layer as the third electrode 105 (a region denoted by A inFIG. 13), the common electrodes 401 provided in one pixel areelectrically connected to one another.

Note that this embodiment mode shows an example where the descriptionsin Embodiment Modes 1 to 3 are realized together with a transistor andwhich is a modification of those in Embodiment Modes 4 to 15. Therefore,the descriptions in Embodiment Modes 1 to 15 can be applied to orcombined with this embodiment mode.

The structure of the pixel portion of this embodiment mode can be freelycombined with the foregoing embodiment modes.

Embodiment Mode 17

In this embodiment mode, a top view of a pixel portion different fromthat described in the foregoing embodiment mode is described.

FIG. 14 is different from FIG. 13 in that the comb-shaped firstelectrode 103 and the comb-shaped third electrode 105 are bent at thecenter point of the long side. The electrodes may be bent at anotherpoint instead of the center point. In addition, they may have aplurality of bends. Such the bent first electrode 103 and the bent thirdelectrode 105 are preferable since they can widen a viewing angle. It isbecause some of the liquid crystal molecules follow a first direction ofthe bent first electrode 103 and the third electrode 105, and some ofthe liquid crystal molecules follow a second direction thereof.

Alternatively, in order to obtain the same effect, one pixel may bedivided into two regions by the center line, and in a first region, thestraight first electrode 103 and the straight third electrode 105 arearranged with a certain angle, and in a second region, the straightfirst electrode 103 and the straight third electrode 105 are arranged soas to be symmetric with respect to the central line.

Note that this embodiment mode shows an example where the descriptionsin Embodiment Modes 1 to 3 are realized together with a transistor andwhich is a modification of those in Embodiment Modes 4 to 16. Therefore,the descriptions in Embodiment Modes 1 to 16 can be applied to orcombined with this embodiment mode.

Embodiment Mode 18

In this embodiment mode, a structure of the liquid crystal displaydevice which is different from that shown in FIG. 1 in that a reflectiveregion A and a transmissive region B are provided is described.

As shown in FIG. 15, a reflective electrode 652 is provided in thereflective region. In the transmissive region, a transparent electrode654 connected to the reflective electrode 652 is provided. Thetransparent electrode 654 also serves as a common electrode. Inaddition, the counter substrate 155 is provided thereover with a liquidcrystal material 653 interposed therebetween.

In addition, a retardation film 650 is placed over an outer side of thecounter substrate 155 provided over the liquid crystal material 653.That is, the retardation film 650 is placed between the countersubstrate 155 and the polarizing plate. A quarter-wave plate and ahalf-wave plate are given as a retardation film. With the retardationfilm, an amount of light which passes the reflective region and thetransmissive region can be appropriately controlled. Therefore,approximately the same image can be displayed whether the liquid crystaldisplay device is transmissive or reflective.

The description of other structures is omitted because it is similar tothat of FIG. 1.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 17 can be applied toor combined with this embodiment mode.

Embodiment Mode 19

In this embodiment mode, a structure which is different from thatdescribed in the foregoing embodiment mode in that the retardation filmis provided inside the counter substrate is described.

As shown in FIG. 16, the retardation film 650 is formed inside thecounter substrate 155, that is, the side of the liquid crystal material653. With such a structure, an amount of light which passes thereflective region and the transmissive region can be appropriatelycontrolled. Therefore, approximately the same image can be displayedwhether the liquid crystal display device is transmissive or reflective.

Description of other structures is omitted because it is similar to thatof FIG. 15.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 18 can be applied toor combined with this embodiment mode.

Embodiment Mode 20

In this embodiment mode, a structure in which a cell gap in thereflective region and the transmissive region is controlled isdescribed.

As shown in FIG. 17, a film 657 for adjusting a cell gap is provided onthe counter substrate 155 side. An alignment film is formed over thefilm 657 (on the side closer to the liquid crystal). Such a film 657 isformed of an organic material such as acrylic. The cell gap is set sothat the cell gap in the reflective region is shorter than that in thetransmissive region. With such a structure, an amount of light whichpasses the reflective region and the transmissive region can beappropriately controlled. Therefore, approximately the same image can bedisplayed whether the liquid crystal display device is transmissive orreflective.

The description of other structures is omitted because it is similar tothat of FIG. 15.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 19 can be applied toor combined with this embodiment mode.

Embodiment Mode 21

In this embodiment mode, a structure which is different from thatdescribed in the foregoing embodiment mode in that light scatteringparticles are contained in the film for adjusting a cell gap.

As shown in FIG. 18, light scattering particles 658 are contained in thefilm 657 for adjusting a cell gap. The light scattering particle 658 isformed of a material with a refractive index different from that of thefilm for adjusting a cell gap. The film for adjusting a cell gap may beformed so as to contain such light scattering particles.

With such a structure, light can be diffused and luminance can beimproved.

The description of other structures is omitted because it is similar tothat of FIG. 15.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 20 can be applied toor combined with this embodiment mode.

Embodiment Mode 22

In this embodiment mode, a structure which is different from that shownin FIG. 1 in that a reflective region is provided is described.

As shown in FIG. 19, in this embodiment mode, a reflective liquidcrystal display device is shown in which an electrode formed at the sametime as the gate electrode 113 is used as the reflective electrode 652.The reflective electrode 652 is placed so as to be approximatelyparallel to the gate wire, whereby an efficient layout can be achieved.In addition, since the reflective electrode 652 can be formed at thesame time as the gate wire, the number of steps can be reduced and thecost can be reduced.

Note that description in Embodiment Modes 1 to 21 can be applied to orcombined with this embodiment mode.

Embodiment Mode 23

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 22 in that the reflective region and atransmissive region are provided is described.

As shown in FIG. 20, in this embodiment mode, a structure of thesemi-transmissive liquid crystal display device is shown in which anelectrode formed at the same time as the gate electrode 113 is used asthe reflective electrode 652. The reflective electrode 652 can serve asa common wire. The reflective electrode 652 is placed so as to beapproximately parallel to the gate wire, whereby an efficient layout canbe achieved. In addition, since the reflective electrode 652 can beformed at the same time as the gate wire, the number of steps can bereduced and the cost can be reduced.

Note that the description in Embodiment Modes 1 to 22 can be applied toor combined with this embodiment mode.

Embodiment Mode 24

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 23 in that a manufacturing order of thereflective electrode and the transparent electrode is changed isdescribed.

As shown in FIG. 21, the transparent electrode 654 is formed first andthe reflective electrode 652 is formed over a part of the transparentelectrode 654. Then, the electrode 117 is connected to the reflectiveelectrode 652.

With such a structure, the reflective electrode 652 can be formed at thesame time as the gate electrode 113. The reflective electrode 652 can beused as the common wire. The reflective electrode 652 is placed so as tobe approximately parallel to the gate wire, whereby an efficient layoutcan be achieved. In addition, since the reflective electrode 652 can beformed at the same time as the gate wire, the number of steps can bereduced and the cost can be reduced.

Description of other structures is omitted because it is similar to thatof FIG. 20.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 23 can be applied toor combined with this embodiment mode.

Embodiment Mode 25

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 24 in that the transparent electrode is notprovided is described.

As shown in FIG. 22, the reflective electrode 652 is formed in thereflective region but not in the transmissive region. The electrode 117is connected to the reflective electrode 652.

With such a structure, the reflective electrode 652 can be formed at thesame time as the gate electrode 113. The reflective electrode 652 can beused as the common wire. The reflective electrode 652 is placed so as tobe approximately parallel to the gate wire, whereby an efficient layoutcan be achieved. In addition, since the reflective electrode 652 can beformed at the same time as the gate wire, the number of steps can bereduced and the cost can be reduced.

The description of other structures is omitted because it is similar tothat of FIG. 21.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 24 can be applied toor combined with this embodiment mode.

Embodiment Mode 26

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 22 in that a conductive layer 659 serving asthe common wire is provided is described.

As shown in FIG. 23, the conductive layer 659 is formed over the baselayer 101 in the reflective region. The conductive layer 659 can beformed at the same time as the gate electrode. The electrode 117 servingas the reflective electrode connected to the conductive layer 659 isformed.

With such a structure, the conductive layer 659 can be used as thecommon wire. The conductive layer 659 is placed so as to beapproximately parallel to the gate wire, whereby an efficient layout canbe achieved. In addition, since the conductive layer 659 can be formedat the same time as the gate wire, the number of steps can be reducedand the cost can be reduced.

The description of other structures is omitted because it is similar tothat of FIG. 19.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 25 can be applied toor combined with this embodiment mode.

Embodiment Mode 27

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 26 in that the conductive layer 659 serving asthe common wire is provided in the reflective region and a transmissiveregion is provided is described.

As shown in FIG. 24, the conductive layer 659 is formed over the baselayer 101 in the reflective region, and the electrode 117 serving as thereflective electrode connected to the conductive layer 659 is formed. Inthe transmissive region, the transparent electrode 654 connected to theelectrode 117 is formed.

With such a structure, the conductive layer 659 can be used as thecommon wire. The conductive layer 659 is placed so as to beapproximately parallel to the gate wire, whereby an efficient layout canbe achieved. In addition, since the conductive layer 659 can be formedat the same time as the gate wire, the number of steps can be reducedand the cost can be reduced.

The description of other structures is omitted because it is similar tothat of FIG. 23.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 26 can be applied toor combined with this embodiment mode.

Embodiment Mode 28

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 27 in that a manufacturing order of thereflective electrode and the transparent electrode is changed isdescribed.

As shown in FIG. 25, the transparent electrode 654 is formed first andthe electrode 117 serving as the reflective electrode is formed over apart of the transparent electrode 654.

With such a structure, the conductive layer 659 can be used as thecommon wire. The conductive layer 659 is placed so as to beapproximately parallel to the gate wire, whereby an efficient layout canbe achieved. In addition, since the conductive layer 659 can be formedat the same time as the gate wire, the number of steps can be reducedand the cost can be reduced.

The description of other structures is omitted because it is similar tothat of FIG. 24.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 27 can be applied toor combined with this embodiment mode.

Embodiment Mode 29

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 28 in that the conductive layer 659 serving asthe common wire is formed in the reflective region and the transparentelectrode is not provided is described.

As shown in FIG. 26, the conductive layer 659 is formed in thereflective region while an electrode is not formed in the transmissiveregion. The electrode 117 serving as the reflective electrode isconnected to the conductive layer 659.

With such a structure, the conductive layer 659 can be used as thecommon wire. The conductive layer 659 is placed so as to beapproximately parallel to the gate wire, whereby an efficient layout canbe achieved. In addition, since the conductive layer 659 can be formedat the same time as the gate wire, the number of steps can be reducedand the cost can be reduced.

The description of other structures is omitted because it is similar tothat of FIG. 25.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 28 can be applied toor combined with this embodiment mode.

Embodiment Mode 30

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 29 in that a transparent electrode is formedin the transmissive region is described.

As shown in FIG. 27, the conductive layer 659 is formed in thereflective region while the transparent electrode 654 connected to theconductive layer 659 is formed in the transmissive region. The electrode117 is connected to the conductive layer 659. The conductive layer 659serves as the reflective electrode and as the common wire.

With such a structure, the conductive layer 659 can be used as thecommon wire. The conductive layer 659 is placed so as to beapproximately parallel to the gate wire, whereby an efficient layout canbe achieved. In addition, since the conductive layer 659 can be formedat the same time as the gate wire, the number of steps can be reducedand the cost can be reduced.

The description of other structures is omitted because it is similar tothat of FIG. 25.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 29 can be applied toor combined with this embodiment mode.

Embodiment Mode 31

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 30 in that a projection and a depression areformed in the insulating layer in the reflective region is described.

As shown in FIG. 28, a projection and a depression are formed in theinsulating layer 106 in the reflective region.

A conductive layer 660 is formed along the projection and the depressionin the insulating layer 106. The conductive layer 660 is formed of ahighly reflective material. The conductive layer 660 may be formed ofthe same material as the electrode 117. Reflectance can be improved withthe conductive layer 660 formed along the projection and the depressionin the insulating layer 106.

The projection and the depression can be formed at the same time asforming a contact hole in the insulating layer 106. Therefore, theprojection and the depression can be formed in the reflective regionwithout additional steps being required.

In the transmissive region, the transparent electrode 654 connected tothe conductive layer 659 is formed. The transparent electrode 654 isalso connected to the conductive layer 660. The conductive layer 659serves as the reflective electrode.

The description of other structures is omitted because it is similar tothat of FIG. 27.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 30 can be applied toor combined with this embodiment mode.

Embodiment Mode 32

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 31 in that a manufacturing order of thereflective electrode and the transparent electrode is changed isdescribed.

As shown in FIG. 29, the transparent electrode 654 is formed first.Then, the conductive layer 659 connected to the transparent electrode654 is formed only in the reflective region. The conductive layer 659serves as the reflective electrode. After that, the projection and thedepression are provided in the insulating layer 106. The conductivelayer 660 is formed along the projection and the depression. Theconductive layer 660 is connected to the conductive layer 659.

The projection and the depression can be formed at the same time asforming the contact hole in the insulating layer 106. Therefore, theprojection and the depression can be formed in the reflective regionwithout additional steps being required.

The description of other structures is omitted because it is similar tothat of FIG. 28.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that description in Embodiment Modes 1 to 31 can be applied to orcombined with this embodiment mode.

Embodiment Mode 33

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 32 in that the transparent electrode is notformed is described.

As shown in FIG. 30, the conductive layer 659 is formed in thereflective region. The conductive layer 659 serves as the reflectiveelectrode. The transparent electrode is not formed in the transmissiveregion. After that, the projection and the depression are provided inthe insulating layer 106. The conductive layer 660 is provided along theprojection and the depression and is connected to the conductive layer659. At this time, a lower surface of the conductive layer 660, that is,a bottom surface of the conductive layer 660 in the depression isentirely in contact with the conductive layer 659.

The projection and the depression can be formed at the same time asforming the contact hole in the insulating layer 106. Therefore, theprojection and the depression can be formed in the reflective regionwithout additional steps being required.

The description of other structures is omitted because it is similar tothat of FIG. 29.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 32 can be applied toor combined with this embodiment mode.

Embodiment Mode 34

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 33 in that the bottom surface of theconductive layer 660 in the depression is partially in contact with theconductive layer 659 is described.

As shown in FIG. 31, a part of the lower surface of the conductive layer660, that is, a part of the bottom surface of the conductive layer 660in the depression is partially in contact with the conductive layer 659.The other part of the bottom surface of the conductive layer 660 is incontact with the base layer 101.

The projection and the depression can be formed at the same time asforming the contact hole in the insulating layer 106. Therefore, theprojection and the depression can be formed in the reflective regionwithout additional steps being required.

Description of other structures is omitted because it is similar to thatof FIG. 31.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that description in Embodiment Modes 1 to 33 can be applied to orcombined with this embodiment mode.

Embodiment Mode 35

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 25 in that an opening is provided in theinsulating layer 107 is described.

As shown in FIG. 32, an opening is formed in the insulating layer 107. Aregion in which the opening is formed is the transmissive region.

With such a structure, a cell gap in the transmissive region can bethickened.

In addition, the conductive layer 659 provided in the reflective regionserves as the reflective electrode and is connected to the thirdelectrode 105 through the electrode 117.

The description of other structures is omitted because it is similar tothat of FIG. 22.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 34 can be applied toor combined with this embodiment mode.

Embodiment Mode 36

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 35 in that a transparent electrode is formedin the transmissive region is described.

As shown in FIG. 33, the transparent electrode 654 is formed in thetransmissive region. The transparent electrode 654 is connected to theconductive layer 659 provided in the reflective region.

With such a structure, a cell gap in the transmissive region can bethickened.

The description of other structures is omitted because it is similar tothat of FIG. 32.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that description in Embodiment Modes 1 to 35 can be applied to orcombined with this embodiment mode.

Embodiment Mode 37

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 36 in that a manufacturing order of thereflective electrode and the transparent electrode is changed isdescribed.

As shown in FIG. 34, the transparent electrode 654 is formed over thebase layer 101. After that, the conductive layer 659 is formed only inthe reflective region. The conductive layer 659 serves as the reflectiveelectrode.

With such a structure, a cell gap in the transmissive region can bethickened.

The description of other structures is omitted because it is similar tothat of FIG. 33.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 36 can be applied toor combined with this embodiment mode.

Embodiment Mode 38

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 37 in that the reflective electrode is formedover the insulating layer 106 is described.

As shown in FIG. 35, an opening is formed in the insulating layer 106and the electrode 117 connected to the conductive layer 659 is formed.The electrode 117 is formed only in the reflective region so as to serveas the reflective electrode. After that, the insulating layer 107 isformed to cover the electrode 117 and the opening is formed in theinsulating layer 107 in the transmissive region.

With such a structure, a cell gap in the transmissive region can bethickened.

The description of other structures is omitted because it is similar tothat of FIG. 34.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 37 can be applied toor combined with this embodiment mode.

Embodiment Mode 39

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 38 in that the projection and the depressionare provided in the insulating layer 106 is described.

As shown in FIG. 36, the conductive layer 659 is provided over the baselayer 101 and the insulating layer 106 is formed to cover the conductivelayer 659. The projection and the depression are formed in theinsulating layer 106 above the conductive layer 659. The conductivelayer 660 is formed along the projection and the depression. Theconductive layer 660 is connected to the conductive layer 659. Theconductive layer 660 may be formed of the same material as the electrode117. At this time, the lower surface of the conductive layer 660, thatis, the bottom surface of the conductive layer 660 in the depression isentirely in contact with the conductive layer 659.

With such a structure, a cell gap in the transmissive region can bethickened.

The description of other structures is omitted because it is similar tothat of FIG. 35.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 38 can be applied toor combined with this embodiment mode.

Embodiment Mode 40

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 39 in that the bottom surface of theconductive layer 660 is partially in contact with the conductive layer659 is described.

As shown in FIG. 37, the projection and the depression are formed in theinsulating layer 106 above the conductive layer 659. The conductivelayer 660 is formed along the projection and the depression. A part ofthe lower surface of the conductive layer 660, that is, a part of thebottom surface of the conductive layer 660 in the depression is incontact with the conductive layer 659. The transparent electrode 654 isprovided to be in contact with the conductive layer 659 and the otherpart of the bottom surface of the conductive layer 660 is in contactwith the transparent electrode 654.

With such a structure, a cell gap in the transmissive region can bethickened.

Description of other structures is omitted because it is similar to thatof FIG. 36.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that description in Embodiment Modes 1 to 39 can be applied to orcombined with this embodiment mode.

Embodiment Mode 41

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 30 in that the conductive layer 660 is incontact with the conductive layer 659 and the transparent electrode 654which are formed over one insulating layer is described.

As shown in FIG. 38, the insulating layer 106 is formed to cover theconductive layer 659 and the transparent electrode 654 which are formedover the base layer 101. The opening is formed in the insulating layer106 so as to expose the conductive layer 659 and the transparentelectrode 654. The conductive layer 660 is formed in the opening so asto be in contact with the conductive layer 659 and the transparentelectrode 654.

With such a structure, the conductive layer 659 can be used as thecommon wire.

The description of other structures is omitted because it is similar tothat of FIG. 27.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 40 can be applied toor combined with this embodiment mode.

Embodiment Mode 42

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 41 in that the opening is formed in theinsulating layer 107 is described.

As shown in FIG. 39, the opening is provided in the insulating layer 107in the transmissive region. The first electrode 103 and the thirdelectrode 105 are partially formed over the insulating layer 106.

With such a structure, the conductive layer 659 can be used as thecommon wire.

The description of other structures is omitted because it is similar tothat of FIG. 38.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 41 can be applied toor combined with this embodiment mode.

Embodiment Mode 43

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 42 in that the projection and the depressionare formed in the insulating layer 106 is described.

As shown in FIG. 40, the projection and the depression are formed in theinsulating layer 106 in the reflective region. The conductive layer 660is formed along the projection and the depression. A part of theconductive layer 660 is connected to the third electrode 105 and anotherpart of the conductive layer 660 is connected to the conductive layer659 and the transparent electrode 654.

With such a structure, the conductive layer 659 can be used as thecommon wire.

The description of other structures is omitted because it is similar tothat of FIG. 39.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 42 can be applied toor combined with this embodiment mode.

Embodiment Mode 44

In this embodiment mode, a structure which is different from that shownin FIG. 2 in that the reflective region and the transmissive region isprovided and the reflective electrode 652 is formed only in thereflective region is described.

As shown in FIG. 41, the reflective electrode 652 is formed over theinsulating layer 106 in the reflective region. Then, the reflectiveelectrode 652 and the third electrode 105 are connected.

The description of other structures is omitted because it is similar tothat of FIG. 2.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 43 can be applied toor combined with this embodiment mode.

Embodiment Mode 45

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 44 in that the reflective electrode is formedin the insulating layer 106 having the projection and the depression isdescribed.

As shown in FIG. 42, the projection and the depression are formed in theinsulating layer 106 in the reflective region. The reflective electrode652 is formed along the projection and the depression. The reflectiveelectrode 652 and the third electrode 105 are connected.

The projection and the depression can be formed at the same time asforming the contact hole in the insulating layer 106. Therefore, thereflective electrode with the projection and the depression can beformed without additional steps being required.

The description of other structures is omitted because it is similar tothat of FIG. 41.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 44 can be applied toor combined with this embodiment mode.

Embodiment Mode 46

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 44 in that the opening is formed in theinsulating layer 107 is described.

As shown in FIG. 43, the opening is formed in the insulating layer 107in the transmissive region. The reflective electrode 652 is formed overthe insulating layer 106.

The description of other structures is omitted because it is similar tothat of FIG. 41.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 45 can be applied toor combined with this embodiment mode.

Embodiment Mode 47

In this embodiment mode, a structure which is different from that shownin FIG. 2 in that only the reflective region is provided is described.

As shown in FIG. 44, the wire 121 shown in FIG. 2 is not formed and thereflective electrode 652 is formed over the insulating layer 106 in thereflective region.

The description of other structures is omitted because it is similar tothat of FIG. 2.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 46 can be applied toor combined with this embodiment mode.

Embodiment Mode 48

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 47 in that the projection and the depressionare provided in the insulating layer 106 and the reflective electrode isformed along the projection and the depression is described.

As shown in FIG. 45, the projection and the depression are provided onthe surface of the insulating layer 106 in the reflective region. Thereflective electrode 652 is formed along the projection and thedepression. A shape of the projection and the depression formed in theinsulating layer 106 is not necessarily an opening. In addition, theprojection and the depression can be formed at the same time as formingopenings for a source electrode and a drain electrode of a thin filmtransistor. Note that the projection and the depression are formed forenhancing reflectance and any shape may be employed without departingfrom the scope.

The projection and the depression can be formed at the same time asforming the contact hole in the insulating layer 106. Therefore, thereflective electrode with the projection and the depression can beformed without additional steps being required.

The description of other structures is omitted because it is similar tothat of FIG. 44.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 47 can be applied toor combined with this embodiment mode.

Embodiment Mode 49

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 47 in that a projection is formed over theinsulating layer 106 is described.

As shown in FIG. 46, a conductive layer 602 is formed over theinsulating layer 106 in the reflective region. The conductive layer 602can be formed in the same layer as the source and drain electrodes 116.

A projection 603 is formed over the conductive layer 602 to form aprojection and a depression. The projection 603 is formed by patterningan organic layer. A conductive layer 604 is formed to cover theprojection 603. The conductive layer 602 and the conductive layer 604are connected between the projections 603. The conductive layer 604serves as the reflective electrode.

The conductive layer 604 is connected to the third electrode 105 throughthe opening provided in the insulating layer 107.

The description of other structures is omitted because it is similar tothat of FIG. 44.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 48 can be applied toor combined with this embodiment mode.

Embodiment Mode 50

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 49 in that the conductive layer 602 is notformed is described.

As shown in FIG. 47, the projection 603 is formed over the insulatinglayer 106. The conductive layer 604 is formed to cover the projection603. The conductive layer 604 serves as the reflective electrode.

The description of other structures is omitted because it is similar tothat of FIG. 46.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 49 can be applied toor combined with this embodiment mode.

Embodiment Mode 51

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 47 in that the reflective region and thetransmissive region are provided is described.

As shown in FIG. 48, the reflective electrode 652 is formed over theinsulating layer 106 in the reflective region. The transparent electrode654 connected to the reflective electrode 652 is formed in thetransmissive region.

The description of other structures is omitted because it is similar tothat of FIG. 44.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 50 can be applied toor combined with this embodiment mode.

Embodiment Mode 52

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 51 in that a manufacturing order of thereflective electrode and the transparent electrode is changed isdescribed.

As shown in FIG. 49, the transparent electrode 654 is formed in thereflective region and the transmissive region. Then, the reflectiveelectrode 652 connected to the transparent electrode 654 is formed inthe reflective region

The description of other structures is omitted because it is similar tothat of FIG. 48.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 51 can be applied toor combined with this embodiment mode.

Embodiment Mode 53

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 51 in that openings are provided in theinsulating layers 106 and 107 in the transmissive region is described.

As shown in FIG. 50, the opening is formed in the insulating layer 106in the transmissive region. In the reflective region, the reflectiveelectrode 652 is formed over the insulating layer 106. The transparentelectrode 654 connected to the reflective electrode 652 is formed in theopening in the insulating layer 106.

After that, the opening is also formed in the insulating layer 107 inthe transmissive region so as to expose the transparent electrode 654.Parts of the first electrode 103 and the third electrode 105 are formedover the exposed transparent electrode 654.

The description of other structures is omitted because it is similar tothat of FIG. 48.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 52 can be applied toor combined with this embodiment mode.

Embodiment Mode 54

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 51 in that the projection and the depressionare provided in the insulating layer 106 is described.

As shown in FIG. 51, the projection and the depression are provided inthe insulating layer 106 in the reflective region. The reflectiveelectrode 652 is formed along the projection and the depression.Reflectance of the reflective electrode 652 can be enhanced with theprojection and the depression provided.

The projection and the depression can be formed at the same time asforming the contact hole in the insulating layer 106. Therefore, thereflective electrode with the projection and the depression can beformed without additional steps being required.

Then, the transparent electrode 654 is formed in the reflective regionand the transmissive region. The transparent electrode 654 is connectedto the reflective electrode 652 provided in the reflective region. Thetransparent electrode 654 is connected to the third electrode 105.

The description of other structures is omitted because it is similar tothat of FIG. 48.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 53 can be applied toor combined with this embodiment mode.

Embodiment Mode 55

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 51 in that a projection is formed in thereflective region is described.

As shown in FIG. 52, the projection 603 is formed over the insulatinglayer 106 in the reflective region. The conductive layer 604 is formedto cover the projection 603. The conductive layer 604 serves as thereflective electrode.

The transparent electrode 654 is formed in the transmissive region. Thetransparent electrode 654 is connected to the conductive layer 604formed in the reflective region.

The description of other structures is omitted because it is similar tothat of FIG. 48.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 54 can be applied toor combined with this embodiment mode.

Embodiment Mode 56

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 55 in that a manufacturing order of thereflective electrode 652 and the transparent electrode 654 is changed isdescribed.

As shown in FIG. 53, the transparent electrode 654 is formed over thereflective region and the transmissive region. The reflective electrode652 is formed so as to be connected to the transparent electrode 654 inthe reflective region. In this embodiment mode, the reflective electrode652 is formed to be overlapped with a part of the transparent electrode654.

The projection 603 is formed over the reflective electrode 652 in thereflective region. The conductive layer 604 is formed to cover theprojection 603. The conductive layer 604 and the reflective electrode652 are connected between the projections 603.

The description of other structures is omitted because it is similar tothat of FIG. 52.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 55 can be applied toor combined with this embodiment mode.

Embodiment Mode 57

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 56 in that the reflective electrode 652 is notprovided is described.

As shown in FIG. 54, the transparent electrode 654 is formed over thereflective region and the transmissive region. The projection 603 isformed in the reflective region. A part of the projection 603 is formedover the transparent electrode 654.

The conductive layer 604 is formed to cover the projection 603. Theconductive layer 604 serves as the reflective electrode.

The description of other structures is omitted because it is similar tothat of FIG. 53.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 56 can be applied toor combined with this embodiment mode.

Embodiment Mode 58

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 51 in that the projection 603 is formed overthe insulating layer 106 in the reflective region is described.

As shown in FIG. 55, the reflective electrode 652 is formed over theinsulating layer 106 in the reflective region. The projection 603 isformed over the reflective electrode 652. The conductive layer 604 isformed to cover the projection 603.

The description of other structures is omitted because it is similar tothat of FIG. 48.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 57 can be applied toor combined with this embodiment mode.

Embodiment Mode 59

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 58 in that the reflective electrode 652 is notprovided is described.

As shown in FIG. 56, the projection 603 is formed in the reflectiveregion. The conductive layer 604 is formed to cover the projection 603.The conductive layer 604 serves as the reflective electrode.

The description of other structures is omitted because it is similar tothat of FIG. 55.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 58 can be applied toor combined with this embodiment mode.

Embodiment Mode 60

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 59 in that only reflective region is providedis described.

As shown in FIG. 57, only the reflective region is provided and theprojection 603 is formed in the reflective region. The conductive layer604 is formed to cover the projection 603. The conductive layer 604 canbe formed of the same layer as the source and drain electrodes 116.

The description of other structures is omitted because it is similar tothat of to FIG. 56.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 59 can be applied toor combined with this embodiment mode.

Embodiment Mode 61

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 59 in that a conductive layer is formed in thetransmissive region after the projection and the conductive layer isformed in the reflective region is described.

As shown in FIG. 58, the projection 603 is formed in the reflectiveregion. The conductive layer 604 is formed to cover the projection 603.The conductive layer 604 serves as the reflective electrode.

The transparent electrode 654 is formed over the reflective region andthe transmissive region. The transparent electrode 654 is connected tothe conductive layer 604.

The description of other structures is omitted because it is similar tothat of FIG. 56.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 60 can be applied toor combined with this embodiment mode.

Embodiment Mode 62

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 61 in that a manufacturing order of theconductive layer 604 and the transparent electrode 654 is changed isdescribed.

As shown in FIG. 59, the projection 603 is formed in the reflectiveregion. The transparent electrode 654 is formed in the transmissiveregion, covering the projection 603 partially. After that, theconductive layer 604 connected to the transparent electrode 654 isformed in the reflective region. The conductive layer 604 serves as thereflective electrode.

The description of other structures is omitted because it is similar tothat of FIG. 58.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 61 can be applied toor combined with this embodiment mode.

Embodiment Mode 63

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 59 in that the projection 603 is formed in thereflective region and a conductive layer covering the projection 603 isformed in the same layer as the source and drain electrodes isdescribed.

As shown in FIG. 60, the projection 603 is formed in the reflectiveregion. The conductive layer 604 is formed to cover the projection 603.The conductive layer 604 can be formed of the same layer as the sourceand drain electrodes and serves as the reflective electrode.

The description of other structures is omitted because it is similar tothat of FIG. 56.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 62 can be applied toor combined with this embodiment mode.

Embodiment Mode 64

In this embodiment mode, a structure which is different from that shownin FIG. 3 in that the reflective region is provided is described.

As shown in FIG. 61, the wire 131 shown in FIG. 3 is not formed and thereflective electrode 652 is formed over the base layer 101.

The description of other structures is omitted because it is similar tothat of FIG. 3.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 63 can be applied toor combined with this embodiment mode.

Embodiment Mode 65

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 64 in that the reflective region and thetransmissive region are provided is described.

As shown in FIG. 62, the reflective electrode 652 is formed in thereflective region. After that, the transparent electrode 654 is formedin the reflective region and the transmissive region.

The description of other structures is omitted because it is similar tothat of FIG. 61.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 64 can be applied toor combined with this embodiment mode.

Embodiment Mode 66

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 65 in that a manufacturing order of thereflective electrode and the transparent electrode is changed isdescribed.

As shown in FIG. 63, the transparent electrode 654 is formed in thereflective region and the transmissive region. Then, the reflectiveelectrode 652 is formed only in the reflective region.

The description of other structures is omitted because it is similar tothat of FIG. 62.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 65 can be applied toor combined with this embodiment mode.

Embodiment Mode 67

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 65 in that the reflective electrode isselectively formed only in the reflective region is described.

As shown in FIG. 64, the reflective electrode 652 is formed only in thereflective region.

The description of other structures is omitted because it is similar tothat of FIG. 61.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that description in Embodiment Modes 1 to 66 can be applied to orcombined with this embodiment mode.

Embodiment Mode 68

In this embodiment mode, a structure which is different from that shownin FIG. 4 in that the reflective region is provided is described.

As shown in FIG. 65, the conductive layer 402 shown in FIG. 4 is notformed and the reflective electrode 652 is formed in the reflectiveregion. After that, the reflective electrode 652 is covered with a gateinsulating layer 412 of the thin film transistor 160. An opening isformed in the gate insulating layer 412 and the insulating layer 106,and the reflective electrode 652 and the third electrode 105 areconnected through the opening.

With such a structure, the reflective electrode 652 can be used as thecommon wire.

The description of other structures is omitted because it is similar tothat of FIG. 4.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 67 can be applied toor combined with this embodiment mode.

Embodiment Mode 69

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 68 in that the reflective region and thetransmissive region are provided is described.

As shown in FIG. 66, the transparent electrode 654 is formed in thereflective region and the transmissive region. Then, the reflectiveelectrode 652 connected to the transparent electrode 654 is formed onlyin the reflective region. The transparent electrode 654 and thereflective electrode 652 are covered with the gate insulating layer 412.The opening is provided in the gate insulating layer 412 and theinsulating layer 106, and the reflective electrode 652 and the thirdelectrode 105 are connected through the opening.

With such a structure, the reflective electrode 652 can be used as thecommon wire.

The description of other structures is omitted because it is similar tothat of FIG. 65.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 68 can be applied toor combined with this embodiment mode.

Embodiment Mode 70

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 68 in that the reflective electrode isselectively formed only in the reflective region is described.

As shown in FIG. 67, the reflective electrode 652 is formed selectivelyformed only in the reflective region. The reflective electrode 652 iscovered with the gate insulating layer 412. The opening is provided inthe gate insulating layer 412 and the insulating layer 106, and thereflective electrode 652 and the third electrode 105 are connectedthrough the opening.

With such a structure, the reflective electrode 652 can be used as thecommon wire.

The description of other structures is omitted because it is similar tothat of FIG. 65.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 69 can be applied toor combined with this embodiment mode.

Embodiment Mode 71

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 69 in that the opening is formed in theinsulating layer 106 in the transmissive region is described.

As shown in FIG. 68, the transparent electrode 654 is formed in thetransmissive region and the reflective region. Then, the reflectiveelectrode 652 is selectively formed only in the reflective region. Thetransparent electrode 654 and the reflective electrode 652 are coveredwith the gate insulating layer 412.

The opening is formed in the insulating layer 106 in the transmissiveregion. In the opening, parts of the first electrode 103 and the thirdelectrode 105 are formed over the gate insulating layer 412.

With such a structure, the reflective electrode 652 can be used as thecommon wire.

The description of other structures is omitted because it is similar tothat of FIG. 66.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 70 can be applied toor combined with this embodiment mode.

Embodiment Mode 72

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 69 in that the opening is formed in theinsulating layer 106 in the transmissive region and the transparentelectrode is not formed is described.

As shown in FIG. 69, the reflective electrode 652 is formed only in thereflective region. The reflective electrode 652 is covered with the gateinsulating layer 412.

The opening is formed in the insulating layer 106 in the transmissiveregion. In the opening, parts of the first electrode 103 and the thirdelectrode 105 are formed over the gate insulating layer 412. In thisembodiment mode, the transparent electrode is not formed in thetransmissive region.

With such a structure, the reflective electrode 652 can be used as thecommon wire.

The description of other structures is omitted because it is similar tothat of FIG. 66.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 71 can be applied toor combined with this embodiment mode.

Embodiment Mode 73

In this embodiment mode, a structure which is different from that shownin FIG. 5 in that the reflective region is provided is described.

As shown in FIG. 70, the conductive layer 502 shown in FIG. 5 is notformed and the reflective electrode 652 is formed in the reflectiveregion. The reflective electrode 652 is provided over the gateinsulating layer 412 of the thin film transistor 160. The opening isformed in the insulating layer 106, and the reflective electrode 652 andthe third electrode 105 are connected through the opening.

The conductive layer 601 is formed as a common wire. The conductivelayer 601 is connected to the third electrode 105 through the opening inthe gate insulating layer 412 and the insulating layer 106.

The description of other structures is omitted because it is similar tothat of FIG. 5.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 72 can be applied toor combined with this embodiment mode.

Embodiment Mode 74

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 73 in that a projection is provided in thereflective region is described.

As shown in FIG. 71, a conductive layer 661 is formed in the reflectiveregion. The conductive layer 661 can be formed of the same layer as thesource and drain electrodes 116.

The projection 603 is formed over the conductive layer 661. Theconductive layer 604 is formed to cover the projection 603. Theconductive layer 604 serves as the reflective electrode. The conductivelayer 604 and the conductive layer 661 are connected between theprojections 603.

The opening is formed in the insulating layer 106 provided to cover theconductive layer 604. The conductive layer 604 and the third electrode105 are connected through the opening.

The description of other structures is omitted because it is similar tothat of FIG. 70.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 73 can be applied toor combined with this embodiment mode.

Embodiment Mode 75

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 74 in that the conductive layer 661 is notformed is described.

As shown in FIG. 72, the projection 603 is formed over the gateinsulating layer 412 in the reflective region. The conductive layer 604is formed to cover the projection 603. The opening is formed in theinsulating layer 106 provided to cover the conductive layer 604. Theconductive layer 604 and the third electrode 105 are connected throughthe opening.

The description of other structures is omitted because it is similar tothat of FIG. 71.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 74 can be applied toor combined with this embodiment mode.

Embodiment Mode 76

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 73 in that the transmissive region and thereflective region are provided and the reflective electrode is formedonly in the reflective region is described.

As shown in FIG. 73, the reflective electrode 652 is selectively formedover the gate insulating layer 412 only in the reflective region. Then,the transparent electrode 654 is formed in the reflective region and thetransmissive region.

With such a structure, the conductive layer 601 formed at the same timeas the gate electrode 113 can be used as the common wire.

The description of other structures is omitted because it is similar tothat of FIG. 70.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 75 can be applied toor combined with this embodiment mode.

Embodiment Mode 77

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 76 in that the reflective electrode is formedonly in the reflective region and the transparent electrode is notformed is described.

As shown in FIG. 74, the reflective electrode 652 is selectively formedover the gate insulating layer 412 only in the reflective region. Thetransparent electrode 654 is not formed in the transmissive region.

With such a structure, the conductive layer 601 formed at the same timeas the gate electrode 113 can be used as the common wire.

The description of other structures is omitted because it is similar tothat of FIG. 73.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 76 can be applied toor combined with this embodiment mode.

Embodiment Mode 78

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 77 in that the reflective electrode is formedonly in the reflective region and the projection is formed over thereflective electrode is described.

As shown in FIG. 75, the reflective electrode 652 is selectively formedover the gate insulating layer 412 only in the reflective region. Theprojection 603 is formed over the reflective electrode 652. Theconductive layer 604 is formed to cover the projection 603. Theconductive layer 604 is connected to the third electrode 105.

With such a structure, the conductive layer 601 formed at the same timeas the gate electrode 113 can be used as the common wire.

The description of other structures is omitted because it is similar tothat of FIG. 74.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 77 can be applied toor combined with this embodiment mode.

Embodiment Mode 79

In this embodiment mode, a structure which is different from that inforegoing Embodiment Mode 78 in that the reflective electrode 652 is notformed is described.

As shown in FIG. 76, the projection 603 is formed over the gateinsulating layer 412 in the reflective region. The conductive layer 604is formed to cover the projection 603. The conductive layer 604 servesas the reflective electrode.

With such a structure, the conductive layer 601 formed at the same timeas the gate electrode 113 can be used as the common wire.

The description of other structures is omitted because it is similar tothat of FIG. 75.

In this embodiment mode, tilting of the liquid crystal material can besufficiently controlled by electrical fields generated by two pairs ofelectrodes.

Note that the description in Embodiment Modes 1 to 78 can be applied toor combined with this embodiment mode.

Embodiment Mode 80

The top views shown in FIGS. 13 and 14 show examples where at least oneof the electrode (the first electrode 103) of a liquid crystal elementto which an electric potential is transmitted from the source line andthe electrode (the third electrode 105) of the liquid crystal element towhich an electric potential is transmitted from the common line iscomb-shaped. However, the shapes of the first electrode and the thirdelectrode are not limited to those shown in FIGS. 13 and 14. Forexample, they may be zigzag shaped or wavy shaped. This embodiment modeshows an example of a liquid crystal display device which includes adifferent electrode shape from those shown in FIGS. 13 and 14 withreference to FIGS. 106 and 107.

FIG. 106 shows an example of a liquid crystal display device in whichboth an electrode 204 of a liquid crystal element to which an electricpotential is transmitted from the source line and an electrode 203 ofthe liquid crystal element to which an electric potential is transmittedfrom the common wire are zigzag shaped. Note that although the shape ofthe electrode of the liquid crystal element in the liquid crystaldisplay device in FIG. 106 are different from those in the liquidcrystal display device shown in FIGS. 13 and 14, other structures aresimilar thereto.

In addition, as shown in FIG. 107A, each of the first electrode 103 andthe third electrode 105 may be comb-shaped. Alternatively, as shown inFIG. 107B, either the first electrode 103 or the third electrode 105 maybe comb-shaped and one end of a tooth thereof may be connected to oneend of a neighboring tooth. Further alternatively, as shown in FIG.107C, either the first electrode or the third electrode may becomb-shaped and one end of a tooth may be connected to one end of aneighboring tooth and the other end thereof may be connected to theother neighboring tooth. Still further alternatively, the shape shown in107C may be changed to that in FIG. 107D by connecting one end of thefirst tooth and one end of the last tooth.

With such an arrangement, a rotation direction or the like of the liquidcrystal molecule can be varied by regions in one pixel. That is, amulti-domain liquid crystal display device can be manufactured. Themulti-domain liquid crystal display device can reduce the possibilitythat an image cannot be recognized accurately when seen at a certainangle.

Note that description in Embodiment Modes 1 to 79 can be applied to orcombined with this embodiment mode.

Embodiment Mode 81

A pixel structure included in a liquid crystal display device of thepresent invention is described with reference to the top views of FIGS.13 and 14. A method for leading a wire in the pixel portion may bemodified as long as a circuit shown in FIG. 108 is included therein andit does not depart from the purpose and the scope of the presentinvention. A pixel circuit of a liquid crystal display device of thepresent invention is described with reference to FIG. 108.

In FIG. 108, a gate line 7001 and a source line 7002 intersect. Inaddition, a common wire 7003 a and a common wire 7003 b are ledvertically and horizontally. The gate line 7001 is connected to a gateelectrode of a transistor 7004. In addition, the source line 7002 isconnected to either source or drain electrodes of the transistor 7004.Note that when the liquid crystal display device is an AC driving liquidcrystal display device, the source electrode and the drain electrode ofthe transistor 7004 are switched according to an electric potentialtransmitted from the source line 7002; therefore, the electrodes arereferred to as the source and drain electrodes in this embodiment mode.A liquid crystal element C_(LC) is provided between the source and drainelectrode of the transistor 7004 and the common wire 7003 a. When thetransistor 7004 is in an on state, the electric potential from thesource line 7002 is transmitted to the liquid crystal element C_(LC),while when the transistor 7004 is in an off state, the electricpotential from the source line 7002 is not transmitted to the liquidcrystal element C_(LC). In the case where light needs to pass the liquidcrystal layer although the transistor 7004 is in the off state and theelectric potential from the source line 7002 is not transmitted to theliquid crystal element C_(LC); a capacitor C_(S) is desirably providedin parallel with the liquid crystal element C_(LC). When the capacitorholds voltage, light can pass through the liquid crystal layer even ifthe transistor 7004 is in the off state.

FIG. 109A shows a top view of the display device described in thisembodiment mode. FIG. 109B shows a cross-sectional view corresponding toa line K-L in FIG. 109A. The display device shown in FIGS. 109A and 109Bincludes an external terminal connecting region 852, a sealing region853, and a scan line driver circuit 854 including a signal line drivercircuit.

The display device shown in FIGS. 109A and 109B in this embodiment modeincludes a substrate 851, a thin film transistor 827, a thin filmtransistor 829, a thin film transistor 825, a sealant 834, a countersubstrate 830, an alignment film 831, a counter electrode 832, a spacer833, a polarizing plate 835 a, a polarizing plate 835 b, a firstterminal electrode layer 838 a, a second terminal electrode layer 838 b,an anisotropic conductive layer 836, and an FPC 837. The display deviceincludes the external terminal connecting region 852, the sealing region853, the scan line driver circuit 854, a pixel region 856, and a signalline driver circuit 857.

The sealant 834 is provided to surround the pixel region 856 and thescan line driver circuit 854 provided over the substrate 851. Thecounter substrate 830 is provided over the pixel region 856 and the scanline driver circuit 854. Therefore, the pixel region 856 and the scanline driver circuit 854 are sealed as well as the liquid crystalmaterial by the substrate 851, the sealant 834, and the countersubstrate 830.

The pixel region 856 and the scan line driver circuit 854 provided overthe substrate 851 include a plurality of thin film transistors. In FIG.109B, the thin film transistor 825 in the pixel region 856 is shown asan example.

Note that description in Embodiment Modes 1 to 80 can be applied to orcombined with this embodiment mode.

Embodiment Mode 82

FIGS. 110A and 110B show an example of a module including a liquidcrystal display device of the present invention described in EmbodimentModes 1 to 81. A pixel portion 930, a gate driver 920, and a sourcedriver 940 are provided over a substrate 900. A signal is inputted tothe gate driver 920 and the source driver 940 from an integrated circuit950 through a flexible printed circuit 960. An image is displayed by thepixel portion 930 according to the inputted signal.

Embodiment Mode 83

An electronic appliance including a liquid crystal display device of thepresent invention in its display portion is described with reference toFIGS. 111A to 111H.

FIG. 111A shows a display which has a housing 2001, a support base 2002,a display portion 2003, a speaker portion 2004, a video input terminal2005, and the like. The display portion 2003 includes a liquid crystaldisplay device of the present invention described in Embodiment Modes 1to 82.

FIG. 111B shows a camera which has a main body 2101, a display portion2102, an image receiving portion 2103, an operating key 2104, anexternal connecting port 2105, a shutter 2106, and the like. The displayportion 2102 includes a liquid crystal display device of the presentinvention described in Embodiment Modes 1 to 82.

FIG. 111C shows a computer which has a main body 2201, a housing 2202, adisplay portion 2203, a keyboard 2204, an external connecting port 2205,a pointing mouse 2206, and the like. The display portion 2203 includes aliquid crystal display device of the present invention described inEmbodiment Modes 1 to 82.

FIG. 111D shows a mobile computer which has a main body 2301, a displayportion 2302, a switch 2303, an operation key 2304, an infrared port2305, and the like. The display portion 2302 includes a liquid crystaldisplay device of the present invention described in Embodiment Modes 1to 82.

FIG. 111E shows a portable image reproducing device provided with arecording medium (specifically, a DVD reproducing device), which has amain body 2401, a housing 2402, a display portion A 2403, a displayportion B 2404, a recording medium (e.g., DVD) reading portion 2405, anoperating key 2406, a speaker portion 2407, and the like. The displayportion A 2403 includes a liquid crystal display device of the presentinvention described in Embodiment Modes 1 to 82.

FIG. 111F shows an electronic book which has a main body 2501, a displayportions 2502, an operation key 2503, and the like. The display portion2502 includes a liquid crystal display device of the present inventiondescribed in Embodiment Modes 1 to 82.

FIG. 111G shows a video camera which has a main body 2601, a displayportion 2602, a housing 2603, an external connecting port 2604, a remotecontrol receiving portion 2605, an image receiving portion 2606, abattery 2607, an audio input portion 2608, an operation key 2609, andthe like. The display portion 2602 includes a liquid crystal displaydevice of the present invention described in Embodiment Modes 1 to 82.

FIG. 111H shows a mobile phone which has a main body 2701, a housing2702, a display portion 2703, an audio input portion 2704, an audiooutput portion 2705, an operation key 2706, an external connecting port2707, an antenna 2708, and the like. The display portion 2703 includes aliquid crystal display device of the present invention described inEmbodiment Modes 1 to 82.

As described above, an electronic appliance of the present invention iscompleted by incorporating a liquid crystal display device of thepresent invention in a display portion. Such an electronic appliance ofthe present invention can display an image favorably both indoors andoutdoors. In particular, an electronic appliance such as a camera, animage taking device, or the like which is often used both outdoors andindoors makes the most of advantages that a wide viewing angle and lesscolor-shift due to change in an angle at which a display screen is seencan be achieved both indoors and outdoors.

This application is based on Japanese Patent Application serial no.2005-350147 filed in Japan Patent Office on Dec. 5, 2005, the entirecontents of which are hereby incorporated by reference.

1. A liquid crystal display device, comprising: a substrate; a gateelectrode over the substrate; a first common electrode formed in a samelayer as the gate electrode; an insulating layer over the gate electrodeand the first common electrode; a semiconductor layer over the gateelectrode with the insulating layer therebetween; source and drainelectrodes over the semiconductor layer; a conductive layer being incontact with the first common electrode; a pixel electrode connected toone of the source and drain electrodes; a second common electrodeconnected to the first common electrode with the conductive layertherebetween; and a liquid crystal material over the pixel electrode andthe second common electrode.
 2. The liquid crystal display deviceaccording to claim 1, wherein tilting of the liquid crystal material iscontrolled by an electrical field between the pixel electrode and thefirst common electrode, and an electrical field between the pixelelectrode and the second common electrode.
 3. The liquid crystal displaydevice according to claim 1, wherein the semiconductor layer is anamorphous semiconductor layer.
 4. The liquid crystal display deviceaccording to claim 1, further comprising: a passivation layer over thefirst common electrode and the gate electrode; a color filter over thefirst common electrode with the passivation layer therebetween, and ablack matrix over the source and drain electrodes.
 5. The liquid crystaldisplay device, according to claim 1, wherein the pixel electrode iscomb-shaped.
 6. The liquid crystal display device according to claim 1,wherein the first common electrode is comb-shaped.
 7. The liquid crystaldisplay device according to claim 1, wherein the second common electrodeis comb-shaped.
 8. The liquid crystal display device according to claim1, wherein the pixel electrode is formed of a transparent material. 9.The liquid crystal display device according to claim 1, wherein thefirst common electrode is formed of a transparent material.
 10. Theliquid crystal display device according to claim 1, wherein the secondcommon electrode is formed of a transparent material.
 11. A liquidcrystal display device, comprising: a substrate; a gate electrode overthe substrate; a conductive layer formed in a same layer as the gateelectrode; a first common electrode being in contact with the conductivelayer; an insulating layer over the gate electrode and the first commonelectrode; a semiconductor layer over the gate electrode with theinsulating layer therebetween; source and drain electrodes over thesemiconductor layer; a pixel electrode connected to one of the sourceand drain electrodes; a second common electrode connected to the firstcommon electrode; and a liquid crystal material over the pixel electrodeand the second common electrode.
 12. The liquid crystal display deviceaccording to claim 11, wherein tilting of the liquid crystal material iscontrolled by an electrical field between the pixel electrode and thefirst common electrode, and an electrical field between the pixelelectrode and the second common electrode.
 13. The liquid crystaldisplay device according to claim 11, wherein the semiconductor layer isan amorphous semiconductor layer.
 14. The liquid crystal display deviceaccording to claim 11, further comprising: a passivation layer over thefirst common electrode and the gate electrode; a color filter over thesource and drain electrodes and the first common electrode with thepassivation layer therebetween, a counter substrate provided to face thesubstrate, and a black matrix over the counter substrate.
 15. The liquidcrystal display device, according to claim 11, wherein the pixelelectrode is comb-shaped.
 16. The liquid crystal display deviceaccording to claim 11, wherein the first common electrode iscomb-shaped.
 17. The liquid crystal display device according to claim11, wherein the second common electrode is comb-shaped.
 18. The liquidcrystal display device according to claim 11, wherein the pixelelectrode is formed of a transparent material.
 19. The liquid crystaldisplay device according to claim 11, wherein the first common electrodeis formed of a transparent material.
 20. The liquid crystal displaydevice according to claim 11, wherein the second common electrode isformed of a transparent material.
 21. A liquid crystal display deviceincluding a plurality of pixels, each pixel comprising: a firstreflective common electrode over a substrate; a second transparentcommon electrode over the substrate; an insulating layer over the firstreflective common electrode and the second transparent electrode; apixel electrode over the insulating layer, the pixel electrodecomprising at least a first portion and a second portion; and a thirdcommon electrode over the insulating layer, the third common electrodecomprising at least the first portion and the second portion, whereinthe first portion is located over the first reflective common electrodeand the second portion is located over the transparent common electrode.22. The liquid crystal display device, according to claim 21, whereinthe first reflective common electrode and the second transparent commonelectrode are electrically connected to each other.
 23. The liquidcrystal display device, according to claim 21, wherein the firstreflective common electrode has an uneven surface.
 24. The liquidcrystal display device, according to claim 21, wherein the pixelelectrode is comb-shaped.
 25. The liquid crystal display deviceaccording to claim 21, wherein the first reflective common electrode iscomb-shaped.
 26. The liquid crystal display device according to claim21, wherein the second transparent common electrode is comb-shaped. 27.The liquid crystal display device according to claim 21, wherein thepixel electrode is formed of a transparent material.